Kerr and McEwen both managed bests of 2.36 metres in regular competition, but could not be separated on countback of missed jumps.
They opted for a jump-off, Kerr clearing 2.34m when the American failed after the bar was lowered from 2.38 to 2.36m.
There was a hint of deja vu at the Stade de France as Qatar's Mutaz Essa Barshim had shared Olympic gold with Italian Gianmarco Tamberi in the Covid-hit Tokyo Games three years ago.
The discussion Kerr and McEwen shared with officials was short and to the point: both athletes wanted to continue, there was to be no shared gold.
When McEwen missed his attempt at 2.34m in the jump-off, world indoor champion Kerr had his chance and took it with aplomb.
Barshim took bronze with a best of 2.34m, but Tamberi had a night to forget, finishing 11th in the 12-strong field with a best jump of 2.22m.
