The former Barcelona and Paris Saint-Germain (PSG) attacker, 32, had not played since rupturing his meniscus and anterior cruciate ligament in his left knee while on international duty in October last year.
Neymar, who underwent surgery and a sustained period of rehabilitation, is his country’s all-time leading goalscorer, with 79 goals in 128 appearances.
Named on the Hilal bench for the first time since his injury, he was introduced on 76 minutes of the Asian Champions Elite encounter at a heaving Hazzan Bin Zayed Stadium in Al Ain.
By then, the record four-time Asian champions, who lead the current Saudi Pro League, were 5-3 up, thanks to goals from Renan Lodi and Sergej Milinkovic-Savic, and a Salem Al Dawsari hat-trick.
Neymar cannot be registered for the Saudi top flight until January.
“I need to prepare Neymar with games; that’s the only possible means to bring him to his level, which was the idea today,” Hilal coach Jorge Jesus said.
“There are some risks for the team because we need to use the games to prepare him, but it’s the only way to have one of our important players back at the highest level,” the Portuguese boss added.
On Monday, Hilal took the lead in 26 minutes, when former Newcastle United and Fulham striker Aleksandar Mitrovic played in Lodi down the left, and the ex-Atletico Madrid full-back drilled a low shot past Khalid Essa in the Al Ain goal.
However, Hernan Crespo’s side drew level six minutes before half-time, Morocco international Soufiane Rahimi sliding home a cross.
Rahimi was the star of Al Ain’s Asian Champions League success last season, finishing top scorer and being named player of the tournament.
In first-half stoppage-time, Hilal seemed to take the contest away from their UAE rivals.
First, Joao Cancelo, a summer signing from Manchester City, crossed for Milinkovic-Savic to head home unmarked from six years. Moments later, reigning Asian Player of the Year Al Dawsari raced cleared of the Al Ain defense, skipped around the onrushing Essa, and curled home superbly on the angle.
Al Ain reduced the deficit just after the hour, through substitute Mateo Sanabria, only for Al Dawsari to flick home his second of the night from a Milinkovic-Savic center.
Minutes later, Rahimi notched his double as a see-saw clash took another swing. Al Dawsari then restored Hilal’s two-goal advantage with a sublime strike from range.
Not long into 12 minutes of the allotted injury time, and with Hilal reduced to 10 men after defender Ali Al Bulaihi was sent off for an intentional handball, Rahimi won and converted a penalty to secure his hat-trick and give Al Ain hope, but the Saudi champions hung on to claim the win.
Neymar had little time to truly impact the game, although he did flash wide an effort in the dying moments of normal time.
Hilal sits top of the Western region group, with three victories from three while Al Ain has picked up a solitary point.