Dan Wooden opened the scoring for the Southern League Premier Division South outfit on 44 minutes – but Dan Ajakaiye hit back inside 60 seconds to see the Hornets level at the break.
A Gosport trialist bagged a second half double to consign Horsham to their first loss of the off-season.
The Hornets host near-neighbours Broadbridge Heath on Tuesday evening (7.45pm) before entertaining South Park Reigate this Saturday (3pm).
See some of John Lines’ pictures from the game on this page and the ones linked.
You can read Horsham manager Dominic Di Paola’s thoughts in the West Sussex County Times, out every Thursday.
1. Horsham FC suffer first defeat of pre-season at Gosport Borough - the match in pictures
Action from Gosport v Horsham Photo: John Lines
2. Horsham FC suffer first defeat of pre-season at Gosport Borough - the match in pictures
Action from Gosport v Horsham Photo: John Lines
3. Horsham FC suffer first defeat of pre-season at Gosport Borough - the match in pictures
Action from Gosport v Horsham Photo: John Lines
4. Horsham FC suffer first defeat of pre-season at Gosport Borough - the match in pictures
Action from Gosport v Horsham Photo: John Lines