Substitute Roberto Firmino scored a late goal in stoppage time to grant his side their first win in Group C, which left Tuchel disappointed as he believed that his team deserved to come away with a point.
In a post-match press conference, the German said: "We put in a great performance in the first half. For me, the result was not logical or correct. We conceded two goals in the first half but never at any point did we lose our confidence.
"We played with a lot of bravery and mental strength. Maybe in the second half we gave the ball away too easily but this is Anfield, Jurgen Klopp has worked with his team for three years, Liverpool press you and make it hard. But we never lost our shape.
"Through our efforts we managed to get the equalising goal. But the end was very, very tough."
PSG will be aiming to earn their first Champions League group-stage win when they host Red Star Belgrade in October.