Newcastle, who thrashed Chelsea 4-1 on Saturday, find themselves in a tricky Group F with all four teams in with a chance of progressing to the last 16. Howe remained confident his side could take advantage in Paris.
"The mood of the group is very good, especially after the result at the weekend. The lads did incredibly well to perform at a high level against a very good Chelsea side," the manager told a news conference on Monday.
"We need to play on the edge, that is when we are at our best. I'm going need every ounce of motivation, energy, to get the result. This a defining moment, we are well aware of where we are in the group. And what could happen tomorrow."
Newcastle beat PSG 4-1 in October, however, the Ligue 1 side have won their last six league games, propelling them to the top of the standings, with Howe saying that "since we played them they've been scoring for fun".
"It's hard to talk about their players, the team has quality in every position. We will do our best defensively, our defensive resilience is being good and we are going to try to be as good as we can be."
Bottom-placed Newcastle are just three points behind group leaders Borussia Dortmund, who are on seven, but are running out of time to remain in contention.
"It is imperative we don't lose. This is a defining moment in our Champions League campaign, we are going to give it everything," Howe added.