The loss denied Mariehamn a glorious chance of moving back into second spot in the 12-team Veikkausliiga, a position they could have returned to with a win in the away game played at Saviniemen Jalkapallo Stadium from 1830 hrs.
MYPA went 2-0 up after goals from Olajide Williams on 24 minutes and Espoo born Pekka Shivola on 51 minutes.
Mariehamn was left to chase the game and managed a consolation from Aleksei Kangaskolkka seven minutes past the hour mark.
Kenyan midfielder Amos Chona Ekhalie featured in the entire game in what turned out to be his 20th league from the 22 his team has played this season.
The defeat keeps title hopefuls Mariehamn third on the log with 37 points, four behind leaders Inter Turku. Mariehamn is behind second placed HJK on goal difference.
Triumphant MYPA have now improved to fifth place, two points within Mariehamn.