If you're asking about the passphrase you used to encrypt your wallet.dat containing your private keys then the answer is no. You will still have lost all your private keys contained in wallet.dat - so it is useless to know the passphrase to decrypt the data which you no longer have.

If you're talking about a passphrase that you use to generate a private key as you would with a "brain wallet" then as long as you can remember the passphrase then you should be able to regenerate the private key.