Striker Haldane joined Micky Adams' side on loan in September, even training with the squad after his initial loan spell expired in December.
Haldane, having reached a settlement with Rovers, told Vale's official website: "I'm please with it. I knew my future was not at Bristol Rovers so there was no point being there any longer.
I hope I can do well until the end of the season and see what happens after that.
"I have really enjoyed it here. The boys have made me feel welcome and the staff have been brilliant. Hopefully now I can push on with my career and help Port Vale do well this season."