The controversial Senegalese striker raised eyebrows when teaming up with Leeds manager Neil Warnock in the summer, but has been grabbing the attention for all the right reasons in recent weeks.
Diouf, instrumental in the Yorkshire side's midweek Capital One Cup win over Everton, opened the scoring just after the hour, and although Albert Adomah equalised, he struck again nine minutes from time as Leeds regained the lead.
Midfielder Michael Tonge's thunderbolt clinched Leeds a two-goal advantage with seven minutes remaining and although Adomah's corner deflected off Leeds defender Sam Byram in the 90th minute for an own goal, Warnock's men saw out the remaining minute.
City were dealt a blow just before half-time when defender George Elokobi, making his debut after signing on loan from Wolves on Wednesday, required medical attention following an awkward landing while blocking a cross and was later carried off on a stretcher. Teenager Joe Bryan replaced him.
Striker Jon Stead was the second of three changes for City, while midfielder Neil Kilkenny was back to face his former club.
Goalkeeper Paddy Kenny and skipper Lee Peltier returned to Leeds' starting line-up.
Leeds winger Aidy White tested City goalkeeper Tom Heaton with an early header and Kenny did well to hold Robins striker Ryan Taylor's 20-yard shot in a see-saw opening.
The home side went closest to taking the lead in the 15th minute when Liam Fontaine lashed a close-range volley off target and Kenny was in the right place again soon after to catch Stead's header from Martyn Woolford's free-kick.
Stead fired a 20-yard shot straight at the Leeds goalkeeper and miscued from six yards in the 35th minute either side of Leeds midfielder Rudy Austin's textbook volley, which was comfortably snaffled by Heaton.
Woolford went closest to breaking the deadlock when he headed Richard Foster's inch-perfect cross just wide from eight yards.
But it was Leeds who twice threatened to forge ahead shortly after the restart through Austin.
The Jamaica international first headed Diouf's free-kick against the woodwork with Heaton well beaten and then forced the City keeper into a fine save with another header moments later.
Leeds were not to be denied in the 64th minute however. Byram drilled in a superb low cross from the right and Diouf steered the ball into the far corner.
But the Robins refused to buckle and were back on level terms within six minutes.
Right-back Foster swung over another telling cross and Adomah flung himself at the ball to head powerfully home.
Leeds continued to carry the greater threat though and regained the lead in the 81st minute when Diouf pounced in the penalty area to lash home his second following good work by Luciano Becchio.
The visitors effectively put the game to bed two minutes later when Tonge stepped on to the ball 25 yards from goal and unleashed an unstoppable shot into Heaton's top left-hand corner.
There was still time for City to pull one back when Adomah's corner flew into the net off Byram's head, but Leeds held on.