The Portuguese star was nominated to do the viral charity craze by Darren Fletcher, while the Brazil international asked Camilo Zuniga to follow his lead.
The craze, which involves dumping a bucket of ice water on your head, is intended to aid the ALS Association, and a number of celebrities have been taped doing it.
Ronaldo was nominated by former Manchester United teammate Darren Fletcher and, in turn, challenged American singers Beyonce, Jennifer Lopez and Lil Wayne to follow suit.
Another football star to have joined the fad was Barcelona midfielder Neymar, who was nominated by Brazil teammate Marcelo.
The 22-year-old, successfully did the challenge, posted a video of it to his Instagram account and nominated new Santos signing Robinho. And, with a hint of humor, he also nominated Camilo Zuniga, who injured him when the Selecao faced Colombia in the World Cup earlier this summer.
ALS, also known as motor neurone diswease and Lou Gehrig's disease after the former baseball star whose life it claimed, is a neurodegenerative disease that causes people to lose muscle function.