Ittihad are still in the driver's seat on 59 points, three ahead of Al-Nassr, with five games left to play. Ittihad also have the upper hand in the head-to-head record between the sides this season.
Fahd Al-Rashidi scored once in each half to give Al-Taawoun a 2-0 lead before Abderrazak Hamdallah replied in the 76th minute.
Ronaldo, who has scored 12 league goals since joining Al-Nassr in January, posted a photo on Twitter with Al-Nassr's motto "ANA AALAMY" in Arabic in the early hours on Thursday.