Harps were impressive on their visit to the league’s bottom club, ending up 5-1 winners.
The Donegal men went in just one ahead at the break, thanks to Thomas McBride’s penalty kick after the midfielder was taken down in the box.
SD Galway were taken apart in the second half with Ciaran Coll, McBride, and Thomas Bonner scoring three times in five minutes to make the score 4-0 by the 70th minute.
Ronan Conlon got one back for Galway, but Matt Harkin added a fifth at the end to continue Sligo’s shocking start to the season.
Harps can now enjoy a three week break from the league – and hope to build on this result.