The Ghanaian winger, who made his first team debut in the 2-1 defeat to Livingston at the Tony Macaroni Arena on Saturday, scored a wonder goal in the second half, receiving the ball from a short corner and cutting in from the left before arrowing the ball past Mark Gillespie into the top corner from a tight angle on 70 minutes.
Grant Murray’s side were already two goals down when the on-loan Manchester City youngster reduced arrear.
Adam Livingstone’s first-half strike and a 64th-minute penalty from David Turnbull, after Maciej Dabrowski had brought down George Newell, had Stephen Craigan’s side in control.
It could have been more but the Polish ‘keeper pulled off a series of fine saves to keep the scoreline down.
The capital club had plenty of chances throughout the game with Fraser Murray shooting just wide inside the opening 60 seconds, and Ben Stirling’s header saved well by Gillespie.
Jamie Gullan sent a 30-yard free kick inches wide of the post shortly before the interval while Agyepong continued to threaten during the second period before scoring.
Gullan went close twice in quick succession as Hibs sought an equaliser but Turnbull’s second, and Motherwell’s third, put the game beyond Hibs in the 84th minute, as last season’s development league champions fell to their first defeat of the season.
Hibs: Dabrowski, O’Connor, Waugh, Campbell, Mackie, Stirling, F Murray, Hyndman, Shanley, Gullan, Agyepong. Subs: Martin, Woods, Paton