Short answer

Same mnemonic phrase, derived to multiple chains, yes — that's how MetaMask, Trust Wallet, and most multi-chain wallets work. But the same address does not exist across truly different chains. Bitcoin addresses live on Bitcoin only; Ethereum addresses live on EVM chains (Ethereum + L2s + BNB Chain + Polygon + many forks); Solana addresses are Solana-only. Sending BTC to an Ethereum address is the canonical "lost forever" mistake.

What "same wallet" actually means

A wallet at the BIP-39 level is just a mnemonic — twelve or twenty-four English words. From that mnemonic, BIP-32 and BIP-44 derive different private keys for different "coin types": coin_type 0 is Bitcoin, 60 is Ethereum, 501 is Solana, 145 is Bitcoin Cash. Each coin's derivation produces an entirely separate private-key/address pair, even though they all trace back to the same mnemonic.

So importing the same mnemonic into Ledger Live shows BTC at one address, ETH at a different address, SOL at a third — all "yours," but each living on its own chain.

The EVM family is special

Ethereum, Polygon, Arbitrum, Optimism, Base, BNB Chain, Avalanche C-Chain, Fantom — all use the same address derivation. Your Ethereum address 0xABC... is also your Polygon address, your Arbitrum address, your BNB Chain address. The address shows up on every EVM chain because they all share the same key-to-address derivation rules.

This is convenient but also a frequent source of confusion: holders see their address on multiple chains and wonder why the balance is different. Each chain has its own state — the address is just a pointer; the balance is per-chain.

The fatal mistake

Sending BTC to your Ethereum address. The two chains don't share state. The Bitcoin network rejects the transaction (the address isn't valid Bitcoin format), or if you somehow bypass the format check, the funds are stuck. Exchange withdrawal flows usually validate the address format and refuse mismatched sends, but P2P payments and direct wallet transfers don't always.

Cross-chain workflows

To move value from Bitcoin to Ethereum: use a centralized exchange (sell BTC, buy ETH, withdraw to ETH address) or a decentralized bridge (Thorchain, Wormhole). Bridges carry significant risk — every major bridge has been exploited at some point. For US holders, sticking to CEX for cross-chain moves is usually the safer path.

Further reading: Bridge, Derivation path.