Esperance soaked up constant pressure from Mamelodi Sundowns of South Africa in Pretoria before snatching a 1-0 win to advance 2-0 overall after also winning 1-0 at home.
Mohamed Abdelmonem, Wessam Abou Ali and Akram Tawfik scored in the second half for Ahly, who are seeking a record-extending 12th victory in the premier African club competition.
Raed Bouchniba came off the bench to score 12 minutes into the second half against Sundowns in a match that lasted 190 minutes after a storm halted play midway through the opening half.
It will be the third time Ahly and Esperance face each other in the final of the Champions League with the Egyptians winning in 2012 and the Tunisians succeeding in 2018.
They also clashed in the semi-finals last season with Ahly winning home and away for a 4-0 aggregate triumph.
Both clubs have booked final places after 11 clean sheets in 12 qualifying, group and knockout matches.
Esperance, seeking a fifth Champions League title, will host the first leg in Rades on the outskirts of Tunis on May 18 with the return match in Cairo seven days later.
Sundowns had their chances against Esperance with Peter Shalulile and Aubrey Modiba hitting the woodwork and Namibia captain Shalulile coming close several times.
But the first time Esperance threatened to score they did so as a counterattack ended with Bouchniba racing into the area and firing across goalkeeper Ronwen Williams into the far corner.
Since their lone Champions League title in 2016, Sundowns have reached the semi-finals three times and lost on each occasion to north African opponents.
In Cairo, Joel Beya had a goal for Mazembe early in the second half disallowed before a powerful header from Abdelmonem off a corner broke the deadlock on 68 minutes.
A superb cross from veteran Tunisia defender Ali Maaloul was fired into the net by Abou Ali on 83 minutes for his first goal of the African campaign.
Tawfik struck 12 minutes into added time by racing through and slamming the ball across Senegalese goalkeeper Alioune Faty into the far corner.
© Agence France-Presse
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