Pakistan put down five catches, with Saeed Ajmal dropping three, in an error strewn display.
In total, Pietersen faced 52 balls with two sixes and eight fours as his side finished on 151 for four in reply to Pakistan's 148 for nine.
Pakistan had made a bright start, reaching 50 inside seven overs, but their momentum was lost after the introduction of spin with Graeme Swann picking up the vital wicket of opener Salman Butt, who had made 34 off 26 balls.
Slow left-armer Michael Yardy took two wickets but the second major breakthrough wicket came when Pietersen made a superb running catch in the deep to get rid of Umar Akmal who had reached 30 in 25 balls.
Pakistan's troubles were partially self-inflicted, with skipper Shahid Afridi getting himself out attempting a suicidal run from his first ball.
Afridi's day was to get substantially worse, however, when his team took the field.
England's South African-born opening pair of Michael Lumb and Craig Kieswetter put on 44 for the first wicket.
Kieswetter was dropped in the first over by Ajmal who spilled the same batsman again before giving Lumb a life.
Lumb went in the sixth over, spinner Ajmal redeeming himself partially as he lured the England batsman down the track for a stumping but Pietersen was in the mood for a match-winning display.
At first with Kieswetter and then in a 60-run partnership with Collingwood, Pietersen struck the ball with power and intent.
Strutting around the crease, hampered only for a short while by a sore ankle after he struck his own foot, Pietersen steered England home comfortably.
There were unnecessary nerves at the very end, the departures of Collingwood and Eoin Morgan leaving Luke Wright looking edgy even though the target had become a formality.
"We need one more victory and hopefully we can get to a semi-final," Pietersen said.
"The more you play, the better you get. Twenty20 cricket is serious business now," he said.
Afridi was left to ponder the many errors made by his team.
"You can't afford to miss opportunities and had we taken the opportunities the match could have turned out differently," he said.