As the time passed, Dean Martin was polished as an actor. In late 1950's and early 1960's Dean Martin and Sinatra became close friends. Then they had friendship with some other people such as Joey Bishop, Peter Law ford and Sammy Davis Jr. and they had formed a group known as The Rat Pack. This group was a sort of continuation of another group of social friends named Humphrey Bogart and Lauren Bacall, Sinatra was also a member of this group.

Dean Martin, Sintara, Bishop, Law ford and Davis never ever named themselves as "The Rat Pack". In fact they used to call themselves as "The Summit" or sometimes as "The Clan". This group of people used to make movies together and was a good social group of people in the Hollywood. They were also politically influential at that time as Peter Law ford was married to Patricia Kennedy who was sister of President John. F. Kennedy.

"The Rat Pack" was very much famous for their totally unannounced performances in Las Vegas. People didn't know at that time that how many of them are going to perform. Suppose there would be a notice pasted in a club reading "Performance by Dean Martin may be Sammy, may be Frank". The days when these people were anticipated to perform there were people sleeping even in the hotel lobbies to get a chance to see these three people together. "The Rat Pack" would sing in the act and tell jokes and would mimic each other in various ways. They would make people laugh aloud. People loved to see them together. This made Dean Martin more and more popular with time and people admired his talents as an actor as well as a singer.

The performances by "The Rat Pack" were only in Las Vegas. In a sense these people revolutionized Las Vegas. Dean Martin and Sinatra refused to appear in the casinos which didn't allow Davis to enter as he was an African-American. So, in this way doors of casinos were opened for the African-American people too.