The 34-year-old, who is attempting to force his way back into the England reckoning, reached 53 from 63 balls with the eighth four of his innings off the bowling of Sam Weller shortly after lunch at The Parks.
Surrey were indebted to Pietersen???s contribution after making a disappointing start to the three-day game, with the batsman coming to the crease at 31-2 in the 10th over.
England’s leading run-scorer moved off the mark on his eighth delivery and hit his first boundary after 31 balls.
However, he struggled for support and saw the dismissals of Vikram Solanki, Steven Davis and Jason Roy as Surrey reached lunch on 122-5, with Pietersen unbeaten on 47.
Pietersen has played exclusively Twenty20 cricket in various leagues around the world since being axed by England following the humiliating Ashes whitewash defeat last year.
His last first-class match was in January 2014, when Australia completed a 5-0 thrashing of England in Sydney, and his prior most recent appearance for Surrey was in the LV= County Championship in June 2013.
The pre-season warm-up lacked first-class status, but Pietersen’s inclusion in Surrey’s line-up attracted several hundred spectators and a number of photographers’ long lenses.
Pietersen has given up a deal with Indian Premier League side Sunrisers Hyderabad in order to come back to Surrey as he bids to add to his 104 Test caps with England.