Anderson Talisca scored twice in a 4-2 win over the UAE side in a tense game in Riyadh on Tuesday night.
Talisca gave Al Nassr the lead after 11 minutes when he headed in Marcelo Brozovic's corner, but goals in the 18th and 46th minutes from Shabab Al Ahli star Yahya Al Ghassani put the 2015 runners-up ahead and left the big-spending Saudis on the brink of elimination.
However, Sultan Al Ghannam's 88th-minute header levelled the scores and Talisca put in his second in the fifth minute of injury time to put Al Nassr back in front.
Brozovic then sealed the win two minutes later as Al Nassr secured qualification. The win means Al Nassr joins fellow big-spending Saudi Arabian clubs Al Hilal, Al Ittihad and Al Fahya in the group stage.
The draw for the 32-team tournament, which starts next month, will be made on Thursday in Kuala Lumpur, Malaysia.
It was an impressive effort from Nassr who had endured a difficult start to the Saudi Pro League, losing both their opening games.
After the win, Ronaldo urged his team to keep fighting.
"Difficult game, but important win to qualify for the Asian champions league. Always believe to the end. Never give up," Ronaldo wrote on X, formerly Twitter.
Meanwhile, UAE team's hero Al Ghassani promised to come back stronger. It has been an eventful few months for Al Ghassani who struck the goal that sealed a first top-flight title in seven years for Shabab Al Ahli.
"There is no feeling like playing big matches. I will come back again. Thank you for your continued support," he wrote on X.