Champions PSG had won 18 and drawn two of their opening 20 league games this season, but they came undone on Sunday despite taking the lead through Angel Di Maria's strike in the seventh minute.
Goals from Moussa Dembele and Nabil Fekir turned the match on its head, boosting the confidence of coach Bruno Genesio and president Jean-Michel Aulas before they take on Barcelona in the last 16 of the Champions League on February 19.
"Fear Barcelona? No, no it's not the team's style," coach Genesio told reporters after his side's win over Ligue 1's runaway leaders.
"We were able to apply our game plan. We created a lot of chances in the first half and our equaliser was deserved. We then had the chance to score very early in the second half. We made a block and resisted the Parisian fury.
"We had decided to go and press PSG, look for them high up, and leave spaces behind us. And every time we had the ball, to cause them problems. I don't think they're used to that much in Ligue 1."
More so than the clash with Barcelona, the 52-year-old is preoccupied with catching up in the battle for second place as they sit three points behind current occupiers Lille.
"We needed to take three points to stay close to Lille," he added. "To inflict a first defeat on PSG is rather incidental. The goal is to move forward and to take second place. We remain close to Lille, who are running at full speed."
Meanwhile, president Aulas is confident Lyon can spring another shock against a European heavyweight as their attention turns to Barca, having already beaten Manchester City in the group stage.
"The team played a very good match," Aulas told reporters. "The first half started badly, but we reacted quickly.
"I really take my hat off to the team and to Bruno, who once again selected the right team. Playing with four attackers, as we did, it was ambitious to attack PSG and we made it difficult for them.
"It gives us great satisfaction to stay close to Lille and prepare for the Champions League match against Barcelona, which will be at a similar level.
"PSG looked a bit unnerved by the will and pressing of our players. We may have been thinking about getting closer to Barcelona. It's all great. This is a moment of happiness."