Ronaldo and Marcelo got the goals for Madrid, who have now heaped the pressure on Barcelona.
Real Madrid survived a late scare to edge past Valencia and return to the top of La Liga.
Dani Parejo, a former Real Madrid player, looked to have stolen Valencia a point at the Bernabeu but Marcelo popped up with a late winner to keep Madrid stumbling towards the league title,
Valencia had flown out of the blocks and caused Madrid problems early on but it ended up being, as it so often is, Cristiano Ronaldo who would open the scoring.
Dani Carvajal, who has fair claim to be the best right-back in the world this season, was afforded far too much time to whip over a cross and Ronaldo made no mistake with a thumping header from eight yards.
But when given the opportunity to double their lead from the spot, the Portuguese saw his penalty saved by spot-kick master Diego Alves and Valencia were kept in the game.
Madrid had come so close to going 2-0 up shortly before, as Karim Benzema hit the post, but when the ball came out and Luka Modric had possession, Dani Parejo inexplicably tossed him to the ground and gave away the penalty.
Discarded by the Bernabeu club after coming through the youth system, though, Parejo may have had a crucial say in the title race.
Making up for his earlier mistake, he curled home an 83rd-minute free kick beautifully to stun the Bernabeu into silence and give fresh momentum to Barcelona in the chase for La Liga.
But that lasted just three minutes, with Marcelo bounding forward (despite it being his eighth game in 25 days) and scoring the winner to keep Madrid on track.
It wasn't straightforward but it was a result, and now Zinedine Zidane's men return their focus to the Champions League.