Ronaldo scored a brace in the victory although it took Carlo Ancelotti’s side until after the hour mark to open the scoring through Karim Benzema, following a number of clear cut chances for the visitors.
Gareth Bale started the game on the bench as he recovers from injury, with Real Madrid playing their first game since the winter break Ancelotti’s men took in Qatar.
In what was an especially sluggish first half from Real Madrid it was the visitors who passed up the best opportunity to break the deadlock, with Charles Dias breaking the offside trap to bear down on Diego Lopez. However, the Madrid keeper touched the shot round the post with his defence missing.
Benzema had the first genuine sight of goal for Real Madrid, but he saw his side-footed shot from eight yards out deflected wide of the post by the outstretched leg of David Costas.
Ronaldo and Luka Modric also had sights of goal before Borja Oubina came close to finding the net, craning his neck to meet a bouncing corner kick delivery just yards from goal. However his header drifted over the bar.
As the first half came to a close Madrid were being pressed on to the back foot and Lopez had a real heart in mouth moment when Rafinha’s shot from the edge of the box was deflected inches past the target, with the keeper wrongfooted.
Real Madrid continued to look rusty after the restart, with Ronaldo especially subdued and Celta Vigo passed up another glorious opportunity, with Charles chipping a shot past the post after breaking the offside trap for the umpteenth time.
But the home side finally found the net after 67 minutes when Benzema flicked home a low cross into the box by substitute Jese Rodrguez, who made a positive impact following his introduction off the bench.
Celta Vigo continued to enjoy a degree of freedom in the final third but couldn’t level the score before Ronaldo added Real Madrid’s second, turning into the net at the back post from Dani Carvajal’s cross from the byline.
And Ronaldo scored his 400th goal as a senior player and his 29th of the season in stoppage time, getting himself on the end of Gareth Bale’s pass across the face of goal to cap a performance that betrayed the generous scoreline.