After Carlton Cole had already agreed a four-year deal earlier in the day it was Mears' turn to sign on the dotted line, also on a four-year contract.
Mears started his footballing career as a trainee at Manchester City but only made one first-team appearance before moving to Preston for £200,000.
This deal will cost the Hammers £1 million initially but that may rise to £1.9 million depending on appearances and international caps.
Pardew will now be a happy man after adding another talented, young Englishman to his fast growing squad of mostly home-grown talent.