In 1967, he dropped out of school at age 13 and became a bus driver to help support his family. In early 1978, a staunch anti-Communist, he escaped from the Communist regime of Vietnam by boat and sailed with 87 compatriots to Pulau Besar in Malaysia. In 1978, he received political asylum from the United States and settled in Los Angeles, California. In 1986 he became an American citizen. In 1984 he went on a junket to Las Vegas and played poker for the first time in his life. He continued to go every weekend and lose hundreds of dollars, earning him the nickname "Money Machine". However, he quickly mastered the game, winning his first tournament in 1987. With his poker earnings, he opened a dry cleaning business and furniture store, but sold them in 1990 because they took too much of his time and didn't make enough money. Through these businesses he would, however, meet and work with many Vietnamese people who would fall under his tutelage.
Nguyen met his future wife Van in Vietnam. He eventually brought her to the United States, where they settled in Bell Gardens, California. They have 3 children. Van Nguyen learned poker from her husband. She won the World Poker Tour Celebrity Invitational in March 2008, becoming the first woman to ever win a WPT mixed event.
Nguyen has over 120 finishes in the money from 2000 to 2004, and has won more than 75 tournaments. Nguyen is known for tutoring players, many of whom go on to be successful in their own right, including his cousins David Pham, Minh Nguyen, and his wife Van Nguyen. At one time, Benny Behnen, grandson of Benny Binion, believed Nguyen trained more tournament winners than anyone else. Men receives a portion of some of his students' winnings. In 1991 one of his students gave him the nickname "The Master," and now he is widely known as "Men the Master." He donates a portion of the money he earns through tournaments and tutoring to charities in Vietnam, and in 1996, with the earnings from his final-table finish in the World Series of Poker, built a kindergarten in Vietnam.
Nguyen won the Card Player Magazine Player of the Year award in 1997, 2001, 2003 and 2005 and is widely regarded as one of the most accomplished tournament players in the world. While allegations have been made regarding Nguyen's possible involvement with tournament cheating, nothing has been proven and Nguyen has consistently denied any such actions. As of 2011, his total live tournament winnings exceed $10,300,000. His 72 cashes at the WSOP account for $3,140,780 of those winnings.