Harry Kane's 23rd-minute goal had put leaders Tottenham on course for a fifth away win of the season in the Premier League, but Palace dominated for much of the second half.
Jeffrey Schlupp equalised after a spill by Spurs goalkeeper Hugo Lloris in the 81st minute before Tottenham then finished strongly, only to be denied victory by a string of saves from home keeper Vicente Guaita.
While Tottenham stretched their unbeaten league run to 11 games, a win would have cemented their place at the top.
"I told the players at half-time the exact opposite of what we did in the second half but that's because of what they couldn't do," Mourinho told reporters.
"If I look to the last 10 minutes of the game, [it's two points dropped], if I look at the first 45 minutes, yes, but from 45 to 75 minutes we couldn't play or build from the back and we made lots of mistakes.
"A team like them, they can create and fight in the box. If I split the game into three parts -- we lost two points."
Mourinho refused to blame Lloris for Schlupp's equaliser after the goalkeeper could only parry out Eberechi Eze's in-swinging free kick.
"My goalkeeper is the best goalkeeper in the Premier League, the best in the Premier League period. If I have to blame anyone, it's the team," Mourinho said.
"He should be back for Wednesday [at Liverpool]," he said.