The Portuguese coach last suffered a league defeat in front of his own fans when Porto lost to visiting Beira Mar on February 23, 2002 and since then he has gone unbeaten in 148 games with Porto, Chelsea, Inter Milan and Real.
His 100 percent home record since arriving at the Bernabeu moved on to 12 wins from 12 with first-half goals from Karim Benzema and Ricardo Carvalho that put Real on 60 points.
Third-placed Valencia slipped further behind on 48 points after they were held to a 0-0 draw at home by Sporting Gijon on Saturday.
In the late game, Sergio Aguero scored a superb solo effort to earn Atletico Madrid a 1-0 win at Real Zaragoza that ended a run of four straight defeats.
Zaragoza hit the bar in the closing minutes but Atletico hung on to climb to seventh with 33 points.
REPEAT FEARED
Real were without suspended goalkeeper Iker Casillas and rested the likes of Pepe, Mesut Ozil and Xabi Alonso ahead of Tuesday's Champions League last 16 trip to Olympique Lyon, but still took the lead after only six minutes through Benzema.
Levante suffered an 8-0 drubbing in the King's Cup on their last visit to the Bernabeu two months ago and must have feared a repeat performance.
France striker Benzema had opened the scoring in the same minute back in December and this time he simply provided the finish after some great wing play from Angel Di Maria, who had skipped between three defenders before crossing.
Levante appeared more concerned with avoiding another mauling than getting back into the game and Real's second did not arrive until just before the break when Carvalho turned in Cristiano Ronaldo's free-kick from close range.
Real's youth team goalkeeper Antonio Adan, making his first start for the side, barely touched the ball.
"These games before Champions League matches are always difficult because people aren't focused, especially against a team who lost by a large margin the last time they visited," Mourinho added.
"We got an early goal and from then were able to control the game."
At the Mestalla, Sporting, who had ended Barca's 16-match winning streak with a 1-1 draw last weekend, put in another disciplined display to deny Valencia.
Unai Emery's side were feeling the effects of a midweek Champions League 1-1 draw at home to Schalke 04 and failed to put much pressure on Sporting's goal until the final minutes.
A fierce drive from substitute Jonas straight at the keeper at the end sealed a frustrating night for the home side who had striker Aritz Aduriz carried off with an ankle injury.
