Louis Walker scored 21 points, Justin Griffin had 14 and Kiza Sekiyoba added 13 to lead Hamilton past Grant, 65-47, in the City Section Division II championship game at Cal State Dominguez Hills.
Gio Quintero scored the Lancers' first eight points and they led 11-4 early, but second-seeded Hamilton responded with a 15-2 run to lead 19-13 at the end of the first quarter.
It was all Yankees from there, as they held third-seeded Grant to six points in the third quarter.
Tal Gonen scored 16 points and Quintero and Alex McQueen each added eight for the Lancers (17-14), who were trying to win their first City title in 29 seasons under head coach Howard Levine.
"After the first four minutes they asserted themselves," said Levine, who led Grant to the City 3A final in 1988 and the Division III final in 2012. "They had enough outside shooting where we couldn't double down. I'm not frustrated at all. Every loss is tough, whether it's the [City] finals or in summer league."
Hamilton won its second City title in three years under head coach Mark Mizuno. The Yankees (13-16) defeated Poly to win the Division III title in 2013 and lost to Eagle Rock in last year's Division III final.
Hamilton finished sixth out of seven teams in the Western League behind Fairfax, Westchester, Palisades, University and LACES.
"We play in the toughest league in the City," Griffin said. "All those losses made us be more competitive and gave us a vendetta. Our coach told us to watch their outside shooter No. 43 [Gonen]. Once he cooled down we took control."