Chelsea King, 17, disappeared in her native Poway, near San Diego, California last week (beg22Feb10) and her family has launched an internet campaign in a bid to help locate her.
Cook has now joined the search efforts by posting details of the case on his Twitter.com page.
The funnyman published a link to a website dedicated to finding Chelsea and urged his fans to report any possible sightings.
He writes, "Do u (sic) know this missing girl? 17 years old gone since 2/25/10 - San Diego area - please help find her - www.findchelsea.com."