The 23-year-old from Westmeath beat Gadzhimagomedov on a unanimous 5-0 points decision in the Ukraine decider.
Kurt Walker and Brendan Irvine had to settle for bronze medals after losing their semi-finals on Friday.
Lisburn bantamweight Walker was beaten by Mykola Butsenko while Belfast flyweight Irvine lost to Niall Farrell.
Walker and Irivine were both defeated on a unanimous decision.
Belfast light-welterweight Sean McComb missed out on a bronze medal after losing to England's Luke McCormack in the 64kg division on Wednesday.
McComb suffered a narrow 3-2 split decision loss in the 64kg division.
All four Irish boxers have ensured a place at August's World Championships in Hamburg by virtue of having reached the last 16.
Ireland's Joe Ward has won a third European Championship light heavyweight gold medal after defeating Russia's Muslim Gadzhimagomedov in the final.