Pitman ruled out Robert Koren's strike for Hull, who had to withstand long periods of pressure from the Robins.
For much of the match the hosts created plenty without finding the killer pass, as Marvin Elliot, Nicky Maynard, Albert Adomah and Jamal Campbell-Ryce all saw good chances go to waste.
And the visiting Tigers were grateful to ex-City goalkeeper Adriano Basso, who was in inspired form to produce a string of good saves to deny the home side.
After a quiet start, the hosts had the first effort on target after 11 minutes, when Basso saved Marvin Elliott's attempt.
Aaron McLean had the first sniff for Hull moments later, but veteran Robins goalkeeper David James snuffed out the danger.
Basso was back in action on 18 minutes, producing a superb save to keep out Campbell-Ryce, as the home side had the better of the opening quarter.
Tom Cairney and Koren tried their luck from distance without any success for the visitors, before Albert Adomah made Basso work once again on the half-hour mark.
Keith Millen's side enjoyed the better of the chances throughout the first half, and went close again through Elliott - whose header lacked the power to beat Basso - and Maynard, but the teams went into the break goalless.
After the interval, however, it was Hull who took the lead.
City backed off, allowing Koren and McLean to share a neat one-two to give the Slovenian space in the area. Koren was given time to compose himself and gain his balance before firing low into the bottom corner from 15 yards.
The Robins rallied in their pursuit of a quick equaliser, and only the excellence of Basso prevented Neil Kilkenny from levelling the match just after the hour.
But, with 11 minutes remaining, the home side finally found a way past their former employee.
Cole Skuse's aerial ball fell into the path of substitute Brett Pitman, who bundled the ball beyond Basso and over the line.
Pitman and Adomah tested Basso late on without success, and Cairney fired high and wide for Hull, as City's winless run in all competitions extended to six matches and Hull's three-game winning run came to an end.