After the final whistle on Sunday, social media videos captured Ronaldo cupping his ear before repeatedly pumping his hand forward in front of his pelvic area. The action appeared to be directed at the rival Al Shabab supporters.
In the background, chants of "Messi" could be heard, referencing Ronaldo's long-term football rival from Argentina.
The committee said the Portuguese star would have to pay a fine of 10,000 Saudi riyals (£2,105) to the Saudi Football Federation, and 20,000 riyals (£4,211) to Al-Shabab to cover the costs of the complaint filing fees.
The committee said the decision is not subject to appeal.
In April last year, Ronaldo appeared to grab his genitals while on his way to the dugout following the end of a league game against Al Hilal, which Al Nassr lost 2-0.
