The first half passed without many real chances and despite James Coppinger looking like a lively source of attacking threat from the visitors, his speculative effort 10 minutes before the break never truly tested James Jones.
Theo Robinson then should have put the home side ahead, but fired straight at the goalkeeper when one on one in the only clear-cut chance of the first 45 minutes.
Marc de Val had the home supporters off their seats early in the second half as he tried to lob Jones with a 40-yard free kick, but the visiting goalkeeper scrambled back to tip the cheeky effort over the bar.
In the 65th minute, Paul Gallagher's free kick was blocked and fell at the feet of Chris Humphrey, who lashed a powerful strike into the top corner to put his side ahead.
Cedric Evina forced Jones into a good save as the home side looked for a leveller, but Preston remained a threat on the break and substitute Andrew Little forced Jed Steer into two successive saves with 10 minutes remaining.
With Preston seemingly on their way to their second win of the season, substitute Nathan Tyson pounced after Jones had fumbled the ball and forced it over the line to earn a point for his side.