Paolo Guerrero scored what proved to be the only goal shortly before the half-hour mark, but the Copa Libertadores winners found themselves firmly under the cosh for most of the remaining hour of play.
Al Ahly goalkeeper Sherif Ekramy was guilty of wasting precious time for the Egyptian champions in the second half, delaying his own inevitable substitution due to injury and disrupting his team's rhythm as Ramy Rabia, Mohamed Aboutrika and Walid Soliman attempted to force extra-time.
Rabia had showed his promise in the early stages, racing onto Soliman's free-kick to head just wide of Cassio's goal, but Corinthians soon seized the initiative.
Danilo and Fabio Santos both conspired to miss from close range but Guerrero had the ball in the back of the net in the 29th minute, with the Peruvian heading home Douglas' lofted cross to get the 15,000 travelling Brazilian fans in the party mood.
Al Ahly tried to squeeze in an equaliser before the break but Fabio Santos broke up a fine passing move between Soliman and Ahmed Fathi.
The Egyptians made a positive start to a second period that they went onto dominate, with Soliman slightly over-hitting a pass to Geddo at the far post.
Rabia powered his way into a central position to fire narrowly wide of Cassio's goal following fine work from substitute Aboutrika, but the heavy pressure soon dissipated as Ekramy decided to call time on his own contribution after all.
Fathi struck the side netting from Aboutrika's defence-splitting pass, before the veteran striker saw his own firm effort deflected behind for a corner ahead of Soliman's long-range drive, which dipped wide.
With four minutes remaining, Rabia roamed into the box one final time, finding the space to clip home a late leveller but instead firing over the bar to hand Corinthians a first final appearance since 2000.