It was Dzeko's first goal at the 10th attempt in the Barclays Premier League following his ?27million move in January.
The Bosnian smashed the ball home in the 75th minute following a misplaced clearance by Phil Jones to hand City a 1-0 victory which keeps them on course for Champions League qualification.
Mancini said: "I am sure it will help his confidence. Edin is a fantastic striker.
"He had problems with not playing some games and had difficulties not scoring. But tonight he scored an important goal for us.
"He deserved to score as he is a good guy. It was not easy for him and because of this I will enjoy the moment."
Source: PA
Source: PA