It was always going to be a tough match between sides anxious to keep up their good start to the new season.
Chris Llewellyn could have settled it for Wrexham early in the second half when a mistake in midfield left him with a clear and he beat off two tackles before hitting his rising 15-yard shot against the crossbar.
The home striker was out of luck again 20 minutes from they end when he missed Ryan Valentine's pull-back in the box, and then when Matt Done crossed and Neil Roberts went up for a firm header, Chris Plummer cleared off the line.
Earlier Mark Jones missed a sitter as a deflected Llewellyn shot dropped into his path, giving him time to switch to his left foot and then shot wide with all the net to aim at.
At the other end Jamie Day hit a 40-yard free-kick round the wall giving keeper Mike Ingham a tricky save, down to collect inside his left post.
From a Day corner, Richard Butcher crossed and Plummer headed over the top from close in. Ingham also saved a weak shot from Danny Crow and Butcher later tried an overhead kick that beat the keeper and went wide.
Another free-kick from Day hit beat the wall and left Ingham stranded as it came back off his right post.
Posh fans thought their side had taken the lead when Trevor Benjamin ran on and netted from a missed clearance by the tall Dennis Lawrence, only to have their celebrations cut short by an offside flag.
Apart from the few chances, defences had the advantage with Wrexham relying on a flat back four and Posh stringing five across the back to cancel out most of the threat from the home strikers.