Where to find Onix in HeartGold & SoulSilver

• Cliff Cave — Trade
• Johto Safari Zone — Trade, Walk
• Mt. Silver — Walk
• Mt. Silver Cave — Trade
• Rock Tunnel — Trade, Walk
• Route 47 — Walk
• Union Cave — Trade, Walk
• Victory Road — Walk
• Violet City — Trade

Onix in every game · Johto & Kanto interactive map

By game: Pokémon HeartGold map · Pokémon SoulSilver map