The Tangerines were trailing 2-1 before goals from on-loan defender Curtis Good and midfielder John Rankin turned the match around.
And McNamara was thrilled to see his side rally for a fourth successive win over Killie this season.
He said: "I was delighted with the way the players showed character to come from behind and win the game.
"It was a big win for us, having been 2-1 down. It was a great game and fortunately we came out on top.
"Both teams played good football and all credit to Kilmarnock for playing the way they did.
"They came and passed the ball and have some good players. Alexei Eremenko played well in spells and Kris Boyd is always a threat.
"We were a bit sloppy at times with our passing. We were passing the ball back a lot but once we got back to 2-2 we looked strong again."
Kilmarnock manager Allan Johnston admitted the result was hard to take, adding: "It must have been a great game for the neutral to watch. For large spells, I thought we were the better team.
"I thought Eremenko was different class and we looked a threat with him in the team.
"It was great for him to get 90 minutes under his belt. You can see he has loads of ability.
"To be fair to him, he worked really hard. It's just so disappointing to score two goals at a difficult venue like Tannadice and still lose.
"We've got nothing to show for our efforts after putting so much into the match.
"We just can't afford to lose the goals in the manner in which we did. At the end of the day, it's results that count."