The second-year franchise scored a thrilling 4-3 victory over Chicago Fire at Toyota Park on opening weekend of the 2016 season which Vieira felt was a very promising performance from his side.
"I think it was a really good team performance," said the Frenchman who oversaw his first game in charge of the club.
"I strongly believe we are not at our best at the moment because it was the first game of the league. We will get better and stronger. But I am proud of the team because when we went to a difficult [formation] especially in the last 15-20 minutes, we stuck together and we worked hard."
When asked what impressed him most about the triumph, Vieira added: "That we stuck to our philosophy, the way we want to play football.
"I think at times we played some really good football. I think our play from the back was good. We created chances and that's the way we want to play this year. I was really pleased with that."
Regarding the high-scoring affair, which produced goals from New York's Thomas McNamara, Tony Taylor, Khiry Shelton and Mix Diskerud, Vieira admitted it was always likely to be a game which saw both sides attack freely.
"That was the type of game I was expecting because when I look at Chicago Fire, the games they played in the preseason, we saw a well organized team," he added.
"Those were the type of game we were expecting - difficult games. Both teams I think worked really hard today and we managed to come out on top. That was good.
"It wasn't easy and I am sure that if we keep working hard we will go really well this year."
New York took the lead through midfielder McNamara in the 10th minute with a lovely curling effort from outside the area before the fire levelled through Razvan Cocis less than 10 minutes later.
In the 29th minute, Taylor fired home on the turn to again give New York the lead before Shelton made it 3-1 seven minutes later.
Chicago responded when David Accam played in Kennedy Igboananike four minutes into the second half but Dikserud restored City's two-goal lead just after the hour-mark when volleying home McNamara's clipped ball.
The Fire again managed to get one back through Accam's 72nd-minute penalty after a handball from Shelton but the damage had already been done for Veljko Paunovic's men.