The 31-year-old, who has previously played in Spain for Alcorcon and Granada, joined his parent club in the summer, but has failed to settle in Greece.
"For me, it's an honour and a privilege to sign for Celta Vigo. This is an opportunity for me to return to football of the highest level," said Lopez at his official unveiling.
"I'm here with great enthusiasm to help the club achieve the objective of permanence. Hopefully I can return all the confidence they've placed in me."
Lopez has also played for Atletico Madrid B.