Dean Martin started to sing for some local bands when he was working for an illegal casino. As a singer he named himself "Dino Martini". His first experience of singing was for "Ernie McKay Orchestra ". In early 1940's he met Sammy Watkins and started to sing for him. Sammy Watkins suggested Dean Martin to change his name to "Dean Martin ".

At the age of 24 Dean Martin married Elizabeth Anne McDonald. This marriage ended in 1949 but they had four children during this marriage. According to a source the cause of divorce was constant physical abuse of her wife by Dean Martin. He worked for a number of local bands in early 1940's but the main reason behind his work was his personality and looks until he developed a singing style of his own.

During World War II, Dean Martin was dragged into U.S army in 1944. He served for almost a year in Ohio. He was later reclassified as 4-F and was released from army as he had developed hernia and surgery was needed to get rid of this.

Dean Martin also had links with Mafia early in his carrier. It is said that Mafia bosses arranged for Dean Martin to sing in different clubs and in turn Dean Martin used to sing for these mafia bosses in their parties. Mafia bosses also did Dean Martin other favors as a reward. The mafia bosses related to Dean Martin were Tommy Accardo and Sam Giaconda. Martin used to do small favors for Mafia bosses if they were convenient for him. Federal Bureau of Investigation picked up a Mafioso who had a plan to kill Dean Martin as he had denied doing illegal favors to him. It is also claimed that Dean Martini also had a long term friendship with mafia bosses named Johnny Rosella and Anthony Fiato. In fact, once Anthony Fiato helped Dean Martin in recovering thousands of dollars from two swindlers who had cheated on Dean Martin's Ex-Wife Betty Martin. Besides this Anthony Fiato also did many other favors to Dean Martin.