John Currie pounced to score the 74th-minute goal which gave Ballinamallard United the three points away to 10-man Warrenpoint Town.
Michael McCrudden provided the pass and Currie lifted a cool finish over keeper Jonathan Parr from the left side of the penalty area.
Warrenpoint's Mark Clarke had been sent-off early in the second half.
He was shown a straight red card by referee Evan Boyce for a late challenge on Currie.
"It is great to win away from home on the first day of the season," said Ballinamallard manager Whitey Anderson.
"It was not a game for the purist, a hard, committed encounter and the players had a pure desire to win.
"I am happy with the squad I have and we are going to need everybody."
Last season Ballinamallard managed just one win from their first 11 league fixtures.