Danny Graham had given Championship side Blackburn the lead early.
But Marcus Rashford levelled before Ibrahimovic struck the winner.
And the Swedish striker was pleased with his sides performance.
Manchester United star Zlatan Ibrahimovic was pleased with the win over Blackburn
"It was a good team performance before we came on," Ibrahimovic said.
"We were unfortunate with the goal but we made it 1-1 before the break.
"In the second half me and Paul came in, and he gave a great ball and I scored again.
Manchester United player ratings against Blackburn
Sun, February 19, 2017
Express Sport brings you Manchester United's player ratings from their FA Cup clash with Blackburn Rovers
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Who impressed for Manchester United against Blackburn?
Manchester United star Marcus Rashford scored his side's first of the afternoon
“We are happy with the win.
"We are still in every tournament, we keep going and working hard.
"We get more confidence and now is the decisive moment of the season.”