The shock reverse ended the Spanish champions' unbeaten run of 24 league matches, their longest in 15 years, and was the first time they had lost in La Liga after leading at half time in more than five years.
Coming after last weekend's 1-1 draw at home to Valencia, it also left them five points behind Barcelona after two matches, a significant gap in a competition where the arch rivals often go toe to toe until the season finale.
"Real was very bad, an unacceptable match," a grim-faced Mourinho told a news conference while refusing to single out any player in particular for criticism.
"The only message I want you to take away tonight is that it was a deserved defeat for us," he told reporters.
"This was a match in which the defeat was absolutely deserved. More than two matches with just one point it was a horrible match."
Getafe's equaliser just after halftime, when Juan Valera slipped marker Sergio Ramos and nodded past Iker Casillas from a free kick, would have particularly irked Mourinho given the amount of work the players have been doing on dead ball situations in training.
They also conceded a header in similar circumstances when leading 1-0 against Valencia.
"We have been doing more work than ever on dead ball situations and there is nothing more we can do," Mourinho said.
"We cannot work any harder on organisation," added the Portuguese.
"That goal and the one we conceded against Valencia were two ridiculous goals."
The last time Real stayed winless after two La Liga matches was in the 2001-02 season.
They finished third in La Liga and lost the Copa del Rey final to Deportivo La Coruna but won the Champions League final against Bayer Leverkusen.