A well-taken Ezequiel Lavezzi strike, a David Luiz own goal and a superb solo effort from Javier Pastore condemned the Blues to a convincing defeat at the Parc des Princes, with Eden Hazard converting a 27th-minute penalty.
The Portuguese boss was disappointed with the way his players defended throughout the match, and believed that a lack of concentration cost them the game. He also issued a scathing assessment of the Blues' strikers.
When asked to explain the 'sloppy' goals they conceded, Mourinho responded: "I say ridiculous. You say sloppy, I say ridiculous.
"After the cross comes (for the first goal), we assist the striker and there's no one going for the ball in the crucial position. In the second, it's one of my players on the goal and that's unlucky.
"But the way the team were positioned defensively was not correct. And finally, the third one is even more sloppy. Ridiculous."
He was equally unhappy with the efforts of his frontmen with Andre Schurrle preferred to start as a 'false nine' and Fernando Torres coming off the bench in the second half.
"I'm not happy with my strikers' performances, so I have to try things," Mourinho said.
"With Andre at least I know we have one more player to have the ball, we have one more player to associate with the other players.
"Football is also about scoring goals. That is for strikers, for real strikers. I had to try."
Mourinho refused to concede the tie but admitted that his side will face an uphill task if they want to progress to the Champions League semi-finals.
"It's a difficult job. It's not impossible. Nothing is impossible but it's difficult. They are the kind of team - with the players they have - out of nothing they can score goals. So it will not be an easy job," he said.
"We are not a team full of talent to score lots of goals, especially at this level - but you never know."
The Blues boss revealed why he decided to substitute Schurrle in favour of Torres with the game tied at 1-1.
"I changed it because I thought that Fernando would give us more depth than Andre," he said. "The team was comfortable with Andre, we had good control of the game and good ball possession. Andre was rocking back and the team was quite comfortable controlling the game.
"I thought Fernando would give us a bit more."
PSG boss Laurent Blanc believes the third goal will give the return a different complexion.
"Sometimes it's difficult to concede in the last minute," Blanc said. "It would've been different at 2-1, with an away goal.
"We're aware that 3-1, it will still be a difficult game over there. For the second leg Chelsea will have to attack and we might have some opportunities to play on the counter attack.
"It will be an exciting game but quite a difficult one over there."
PSG may travel to London without Zlatan Ibrahimovic after the striker suffered a hamstring injury midway through the second half.
Blanc said: "He has a muscular problem. He'll probably need to do a few more exams tomorrow.
"We need him, but we had to deal with this situation during the game."
Blanc was pleased with the opening 15 minutes and thrilled with the second-half display.
"This is very encouraging for us. At half-time we were wondering if we were the same level as Chelsea," Blanc said. "We had a very good discussion. We had played 15 very good minutes then nothing.
"The second half was really excellent and we made it really difficult for Chelsea and scored two goals."