The Red Devils' striker Wessam Abou Ali scored an own goal just four minutes into the second half, while substitute José Lopez added a second one minute before the hour mark.
The match was temporarily halted in the 60th minute for about 30 minutes due to adverse weather conditions.
With this loss, Ahly will be desperate for a win when they face Portuguese side FC Porto on Tuesday to keep their hopes of advancing to the next round alive.
Ahly started the match brightly, with midfield trio Marwan Atteya, Hamdi Fathy, and Mohamed Ali Ben Romdhane controlling the center of the park, but they lacked a real attacking threat.
Their shy first-half attempts were easily dealt with by Palmeiras' defense.
On the other hand, the Brazilians applied high pressure and launched several counterattacks, the most notable of which came in the 18th minute, when youngster Estevao eased-past two defenders, but his effort went inches wide of the target.
The game could have taken a turn in the 34th minute when Palmeiras playmaker Raphael Veiga received a direct red card, but the referee reversed his decision after a VAR check.
In the second half, Palmeiras took the lead when Ahly striker Wessam Abou Ali inadvertently deflected a header into his own net in the 49th minute.
The Brazilians nearly added a second six minutes later, but Ahly keeper Mohamed El-Shennawy denied them with a superb save from a free-kick.
Substitute José Lopez made it 2-0 one minute before the hour mark, further complicating Ahly’s challenge.
Just two minutes later, the match was interrupted for around 30 minutes due to adverse weather conditions.
Upon resumption, Ahly made four substitutions—introducing Mohamed 'Afsha' Magdi, Achraf Bencharki, Nejc Gradisar, and Ahmed Ramadan in place of Hamdi Fathy, Trezeguet, Abou Ali, and Achraf Dari—but it was Palmeiras who looked more likely to add to their lead.
Ahly midfielder Marwan Atteya picked up a yellow card and will miss the next game against FC Porto on Tuesday.
Ahly's offensive performance improved slightly, thanks to Moroccan winger Achraf Bencharki, who twice threatened Palmeiras in the closing stages.
Ahly now sit at the bottom of the group with just one point from two matches and will need to secure a win against FC Porto to stay alive in the competition and progress to the round of 16.
Find more details on group standings, match schedules, and competition statistics.
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