The home side were slow out of the traps and paid the price in the third minute when Chris Shuker's cross from the right found Chris Greenacre waiting in the centre to head into the goalkeeper's bottom right corner.
Vale were made to sweat again six minutes later when more inept defending gifted Tranmere far too much room in the box for Shane Sheriff to finally test Joe Anyon from 12 yards.
The Valiants finally came alive in the 17th minute when Rhys Weston's cross was met by Akpo Sodje, but the striker's shot was brilliantly saved by Gavin Ward from close range.
Tranmere pushed on again in the 24th minute and would have replicated their opener if Gareth Taylor could have found the target instead of heading the ball against the crossbar.
Martin Foyle's men were proving to be their own worst enemies when Jason Talbot upended Shuker in the area to concede a penalty.
Former Stoke City player Greenacre subsequently stepped up to the spot and confidently finished to the right of Anyon in the 35th minute.
Port Vale got the goal they deserved only a minute later when Danny Sonner struck a 20-yard shot that took a slight deflection to wrong-foot Gavin Ward before nestling in the back of the net.
Sonner almost levelled the scores in the 61st minute when the ball dropped kindly just inside the area for the midfielder to crack a decent half-volley that forced an impressive save from Ward.
After looking a little lost, Vale regained their grip on the game in the 73rd minute when Sodje's tireless running won him the chance to supply Leon Constantine with a low cross for him to slot home.
Rovers weren't content settling for the draw and took back the lead in the 83rd minute when Shuker's swirling cross was headed past Anyon by Kevin Ellison from 12 yards.