The pup was found on the opposite shore from Conwy town with an eye injury and with no sign of its mother earlier this month.
It was taken to the Welsh Mountain Zoo where its wounds have since healed.
RSPCA inspector Mike Pugh said: "It's fantastic news that this seal pup is on the mend, after such a tough ordeal."
But he urged the public not to approach all lone seals, as they have not necessarily been abandoned by their mothers.
The pup's release has been planned for the first three months of 2017.
A seal pup that was rescued in Conwy county is recovering well and could be released into the wild in the new year, RSPCA Cymru has said.