How to Evolve Onix

Omega Ruby and Alpha Sapphire

Catch an Onix. Onix is a Hidden Pokémon in Granite Cave that can appear after defeating Groudon/Kyogre. You can also find an Onix in the Mirage Caves, which you'll gain access to after obtaining Latios/Latias and the Eon Flute.

Get a Metal Coat. You can find a Metal Coat at New Mauville, in the Generator room. They are also held by wild Magnemite, Skarmory, and Bronzors. You can find wild Magnemite in New Mauville and on Route 110. You can find wild Skarmory on Route 113. You can find Bronzor at Mt. Pyre, but it is a Hidden Pokémon that won't appear until after defeating Groudon/Kyogre.

Give Onix the Metal Coat to hold. You can do this from your Pokémon menu. Onix needs to be holding this item in order to evolve when traded.

Find someone to trade with or get another system. You'll need to trade Onix to another game of Omega Ruby, Alpha Sapphire, X, or Y. If you're trading with a stranger online, make sure that they understand that you need the evolved Steelix traded back afterwards. If you're trading remotely with someone, you'll need to have entered their Friend Code to add them to your list of players. If you're trading with a friend in real life, you just need to be in the same room with wireless enabled for both systems.

Start a trade with your trading partner. You start trading from the PokeNav: Tap the PlayNav button on the right side of the second screen. Open the Player Search System screen. Select the person you're trading with from the Friends or Passersby lists. Tap trade to start the trade process. The other person will be notified.

Trade your Onix to the other player. It will evolve into Steelix immediately upon trading as long as it is holding a Metal Coat.

Have the other player trade your new Steelix back. Once the evolution is complete, have the other player trade Steelix back to you.

Defeat Groudon or Kyogre if you want to get Mega Steelix. You'll need to progress through the story and beat either Kyogre or Groudon before the Steelixite becomes available to find.

Get a Mach Bike. You'll need the Mach Bike in order to reach the Steelixite item. You can get it from Rydel's Cycles. Make sure to pick the Mach Bike, not the Acro Bike.

Travel to the Granite Cave. You'll find the entrance to the cave on Route 106.

Find the Steelixite on floor B2F. You'll find it next to the large lone rock. Use the Mach Bike to get past the crumbling floor tiles.

Give the Steelixite to Steelix to hold. When Steelix is holding the Steelixite, it will be able to evolve into Mega Steelix during battles.

Select “Mega Evolve” in battle to evolve Steelix to Mega Steelix. This will last through the rest of the battle. Mega Steelix will revert to regular Steelix if it is knocked out or the battle ends.

X and Y

Catch an Onix. In both X and Y, you can find Onix in Glittering Cave or on a Rock Friend Safari. In X, you can also get an Onix at Cyllage City.

Find a Metal Coat. You can find one in the Poke Ball Factory, you can win one by playing the Balloon Popping game, and find them held by wild Magnetons. Magnetons can be found in the Lost Hotel and on Friend Safaris (Steel).

Have Onix hold the Metal Coat. It will need to be holding this item in order to evolve into Steelix.

Find a person to trade with or get another system. In order to evolve Onix, it will need to be traded. You can trade with X, Y, omega Ruby, and Alpha Sapphire. If you're trading with someone online, make sure they know you need the Steelix traded back. Consider offering a Pokémon as payment. You'll need to enter Friend Codes to trade online.

Start a trade with your trading partner. You start trading from the PokeNav: Tap the PlayNav button on the right side of the second screen. Open the Player Search System screen. Select the person you're trading with from the Friends or Passersby lists. Tap trade to start the trade process. The other person will be notified.

Trade your Onix. Send the other player your Onix to have it evolve. It will evolve immediately after being traded.

Get your Steelix back. Once you've finished the trade, have the other player trade it back to you. Follow the same process above.

Black 2 and White 2

Capture an Onix. You can find an Onix in many of the caves and tunnels of Black 2 and White 2, including the Relic Passage, Twist Mountain, Clay Tunnel, the Underground Ruins, and Victory Road.

Track down a Metal Coat. You can find a Metal Coat in Chargestone Cave and Clay Tunnel. It can also be purchased on Join Avenue in the Antique Shop, and in Black City.

Give the Metal Coat to Onix to hold. Onix will need to be holding this item in order to evolve into Steelix when traded.

Find someone to trade with. You'll need to trade Onix in order to evolve it. You can trade with Black, White, Black 2, and White 2.

Start a trade with your trading partner. You'll need to be in the same room in order to trade: Point the game port of your DS towards the game port of the other DS. Start the C-Gear on your bottom screen. Tap "IR" and then tap "Trade." Talk to the other player in the room you are taken to in order to start the trade.

Trade Onix. Select Onix as the Pokémon that you want to trade. As soon as the other player accepts, the Onix will be traded and it will evolve into Steelix.

Get your Steelix back. Set up another trade so the other player can trade you back your new Steelix.

Black and White

Obtain an Onix. The only place you'll find an Onix in these games is Relic Castle. You'll have a 15% chance of encountering one at B7F, and it will be between levels 48-50.

Find a Metal Coat. You can get the Metal Coat from the Treasure Hunter on Route 13, and you can find one in Twist Mountain during Winter. It is also held by wild Magnemite, Metang, Metagross, and Bronzong.

Give the Metal Coat to Onix. Onix will need to be holding this item in order to evolve into Steelix.

Find a trading partner. Onix needs to be traded in order to evolve. You can trade with Black, White, Black 2, and White 2.

Start a trade with your trading partner. You'll need to be in the same room in order to trade: Point the game port of your DS towards the game port of the other DS. Start the C-Gear on your bottom screen. Tap "IR" and then tap "Trade." Talk to the other player in the room you are taken to in order to start the trade.

Trade Onix to the other player. Once the player accepts, Onix will be traded and will evolve into Steelix.

Have the other person trade your Steelix back. After the trade and evolution, have the other player trade your Steelix back to you.

HeartGold and SoulSilver

Find an Onix. You can find an Onix in Cliff Cave, Rock Tunnel, at Mt. Silver, on Victory Road, and in the Union Cave. You can also trade a Bellsprout for an Onix in Violet City.

Get a Metal Coat. You'll receive a Metal Coat for finding the gentleman's granddaughter on the S.S. Aqua. You can also find them on wild Magnemites. Maggie in the Kanto Power Plant will give you one as well. You can also win it at the Pokeathlon Dome on Tuesdays, Thursdays, and Saturdays.

Give the Metal Coat to Onix to hold. Onix will need to be holding this item in order to evolve into Steelix.

Find a trading partner. You'll need to trade Onix to evolve it. You can trade with HeartGold, SoulSilver, Diamond, Pearl, and Platinum players.

Start a trade with the other person. You'll need to be in the same room in order to trade: Each player needs to go to the second floor of a Pokémon Center. Talk to the person in the center of the room to enable the wireless communication and enter the trading room. Talk to the player that you want to trade with to start the trade.

Trade your Onix to the other player. As long as it is holding the Metal Coat, it will evolve immediately into Steelix.

Get your new Steelix back from the other person. After the trade is complete, you'll need to get your Steelix back. Repeat the trading process to get Steelix.

Diamond, Pearl, and Platinum

Get an Onix. There are a variety of places you can find an Onix in these games, the most common being Iron Island, Oreburgh Mine, and Victory Road. In Diamond and Pearl, you can also find them at Snowpoint Temple and Stark Mountain. In Platinum, you can also find an Onix at Wayward Cave.

Obtain a Metal Coat in Diamond, Pearl, or Platinum. You can get a Metal Coat from Byron on Iron Island after completing the National Pokedex. They're also held by wild Steelix, Beldum, Bronzor, and Bronzong.

Give the Metal Coat to Onix to hold. Onix will need to be holding this item in order to evolve when traded.

Find someone to trade with. You'll need to find a trading partner to trade your Onix to so that it can evolve into Steelix. You can trade with someone playing Diamond, Pearl, Platinum, HeartGold, and SoulSilver.

Start a trade with your trading partner. You'll need to be in the same room in order to trade: Each player needs to go to the second floor of a Pokémon Center in their game. Talk to the person in the center of the room to enable the wireless communication and enter the trading room. Talk to the player that you want to trade with to start the trade.

Trade Onix to the other player. When prompted to select which Pokémon you'd like to trade, select Onix. The Onix will evolve into Steelix as soon as it is traded.

Have the other player trade you your Steelix back. You'll need to start another trade and have the other person trade you back your new Steelix. Follow the steps above to perform another trade.

Ruby, Sapphire, and Emerald

Trade for an Onix in Ruby, Sapphire, or Emerald. You cannot capture a wild Onix in Ruby, Sapphire, or Emerald, and you can't transfer from Gold, Silver, or Crystal. This means you'll need to trade from FireRed or LeafGreen, which are the only compatible games that also have an Onix.

Find a Metal Coat in Ruby, Sapphire, or Emerald. You'll find Metal Coats held by wild Magnemites and Magnetons. Both of these Pokémon can only be found in New Mauville.

Give the Metal Coat to Onix. Onix will need to be holding this item in order to evolve into Steelix when traded.

Find someone to trade with. You'll need to trade the Onix to someone else to cause it to evolve into Steelix. You can trade with Ruby, Sapphire, Emerald, FireRed, and LeafGreen.

Start a trade with the other person. You'll need to be physically next to the person you want to trade with: Connect the two GBA systems with a Link Cable. Head to the nearest Pokémon Center in both games. It doesn't have to be the same Pokémon Center. Go to the second floor and talk to the person in the middle of the room to start a trading session. Approach the PC in the trading room and select "Trade."

Trade your Onix to the other player. As soon as you both confirm the trade, Onix will be traded and will evolve into Steelix.

Have the other player trade Steelix back. You'll need to have the other player trade Steelix back to you in order to get it. You can start another trade from the trade room.

FireRed and LeafGreen

Catch an Onix. In these two remakes, you can find an Onix in Rock Tunnel or Victory Road, as well as in Sevault Canyon at level 54.

Seek out a Metal Coat in FireRed or LeafGreen. You can find a Metal Coat near the Memorial Pillar in the Sevii islands (post-game), or as a prize from the Trainer Tower.

Give the Metal Coat to Onix to hold. Onix will need to be holding this item in order to evolve when traded.

Find a trading partner. You have to trade Onix to get it to evolve. You can trade with FireRed, LeafGreen, Ruby, Sapphire, and Emerald.

Start a trade with the other person. You'll need to be physically next to the person you want to trade with: Connect the two GBA systems with a Link Cable. Head to the nearest Pokémon Center in both games. It doesn't have to be the same Pokémon Center. Go to the second floor and talk to the person in the middle of the room to start a trading session. Approach the PC in the trading room and select "Trade."

Trade the Onix to the other player. If it is holding the Metal Coat, it will evolve immediately after being traded.

Have the other player trade the Steelix back. After trading and evolving, have the other player trade your the Steelix back so that you can use it.

Gold, Silver, and Crystal

Find an Onix. You can find an Onix in Rock Tunnel, at Mt. Silver, on Victory Road, and in the Union Cave. You can also trade a Bellsprout for an Onix in Violet City.

Get the Metal Coat. You'll receive a Metal Coat for finding the gentleman's granddaughter on the S.S. Aqua. You can also find them on wild Magnemites, and you can get it from Maggie in the Kanto Power Plant in Crystal.

Give the Metal Coat to Onix. Onix needs to be holding this item to evolve when traded.

Find someone to trade with. You'll need to trade Onix in order to evolve it. You can trade with other Gold, Silver, and Crystal players.

Start a trade with the other player. You'll need to be next to each other and have a Link Cable in order to trade: Connect your two systems with the Link Cable. Go to the second floor of any Pokémon Center in each game. Talk to the person on the far left of the counter. Confirm that you want to trade and save your game.

Trade your Onix to the other player. It will evolve immediately after the trade is confirmed on the other payer's system.

Get your Steelix back from the other player. Have the other player initiate another trade and send your Steelix back to you. You can now use your new Steelix.