Reis was born in Portuguese Macau on 20 June 1970. She is of mixed ancestry; her father was Portuguese, and her mother, who is Canton Shanghainese, moved to Hong Kong. Her father, Francis Reis, was born in Hong Kong. He was captured by the Japanese in Hong Kong during World War II. In the concentration camps he was very popular and loved by the other prisoners. However, because of his height, he was sent to work in the mines in Japan until Japan's surrender. After his liberation, he returned to Hong Kong and married Michelle's mother.

In 1973, 3-year-old Michelle Reis was first discovered by shooting a baby ad. In 1982, 12 years old, she took on a second advertisement. During her study, many scouts had stopped her on the road, and offered her casting and shooting commercial film but Reis refused because she wanted to be a FLIGHT attendant. Reis started part- time modelling at the age of 14. She first came to fame when she won the 1988 Miss Hong Kong Pageant at the age of 18. Reis was also the first Miss Chinese International in the same year. Following her Miss Chinese International crowning, she went on to participate in the Miss World 1988 pageant, where she promoted the image of Hong Kong. She was then supposed to compete in the Miss Universe 1989 pageant but withdrew due to health problems.

Reis's parents divorced in 1987. After this time, she rarely contacted her father, who later died in 1995. Reis recalls her childhood as an unhappy one devoid of toys or new clothes. She recalls only her mother's tears and parents' endless bickering, her father gradually coming home less and less, thereby resulting in her being raised by her mother. Many years later after having abandoned his family, Reis's father was thought to have made a phone call to her. By this time, she was already famous. Many years later, Reis recalled this phone call, which left her hurt.

Reis had excellent results when attended Maryknoll Convent School result to 2A (English, Bible) and ranked 7B five-year secondary education graduation exam. Participated in Hong Kong Certificate of Education Examination after shortly she won the 1988 Miss Hong Kong Pageant.

Reis started to build a career within the entertainment industry in the 1990s. She starred in commercials eventually leading to movies. She has also appeared in music videos and TVB television episodes.

Reis married Business tycoon Julian Hui on 23 November 2008, following a very public two-year courtship. Julian was formerly married to Pansy Ho, the daughter of Macau casino businessman Stanley Ho. Their son Jayden Max "JM" Hui was born on 8 February 2011. His is derived from the first initials 'JM' of his parents' names.

Reis has a sister named Yuet Chi who gave birth to a son in September 2010.