The Tauranga boxer squared off against S Falekoono from Auckland in the gold medal contest, with Lee using his height, skills and footwork to good effect.
Despite breaking a bone in his hand in the second round, Garnham carried on with one hand to earn a points decision.
Fellow Tauranga gym mate Jamie Price also had three bouts. Price stopped Jarred Westrupp in his first fight in the middleweight elite male class, with Ben Fui also being stopped in the semifinals. Price faced a huge challenge in the final, meeting New Zealand 2008 Oceania Olympic qualifying representative Daniel Parkin. The fight went down to the wire with Price narrowly losing a split decision.
The third Tauranga boxer, Joseph Otteson, lost a close decision in his quarter-final bout.
The two Golden Gloves medals mean that both Garnham and Price should gain prominent national rankings when the new list is released in a few weeks.