The fifth season of the American television comedy series Rules of Engagement premiered on September 20, 2010. It consisted of 24 episodes, each running approximately 22 minutes in length, marking the first time that the program received a full-season order. CBS initially broadcast the fifth season on Mondays at 8:30 pm ET in the United States between How I Met Your Mother and Two and a Half Men. In February, the show moved to 8:30 ET on Thursdays, following The Big Bang Theory.