The midfielder struck the equaliser for Barca before skipper Carles Puyol powered home a winner.
Iniesta said: "For us to score at the very start of the second half was important. We're happy and it gives us confidence for the upcoming matches.
"We made the correction at the start of the second half. In the first half, they had the ball, and that was key. Valencia have a clear vision of the game, with very good players."