Michael DeCiantis was born in 1900 in Sora, Italy. He was adopted at birth by Sofia and Luigi DeCiantis. His birth parents were Carlo Bruni and Zaiira Morganti. DeCiantis and his adopted family immigrated from Italy to the United States in 1909 and eventually settled in Natick, Rhode Island. In 1915, DeCiantis graduated from West Warwick Grammar School and received a commercial diploma from West Warwick High School in 1920. He attended Boston University Law School from 1921-1923, and clerked in the law firm of Quinn, Kernan, and Quinn. In 1925, DeCiantis was admitted to the Rhode Island Bar. From 1926-1928, he was judge of the probate court of West Warwick, and from 1933-1937 he served as Assistant Attorney General under Attorney General John P. Hartigan. DeCiantis was appointed Chief of the Division of Public Utilities by then Governor Robert E Quinn. DeCiantis held this position from August 1937 August to January 1938. He was also the treasurer of the Democratic State Committee from 1937-1941, and chief counsel of the Rhode Island Unemployment Compensation Board from 1941-1943, while also resuming his private law practice. In 1946, DeCiantis was named town solicitor for West Warwick, a position he held until 1961 when Governor John A. Notte Jr. named DeCiantis to a new five-member Family Court. He served in this role until his retirement in 1978.
In 1930, Michael DeCiantis married Dorothy “Dot” (née Glenn), and the couple had one daughter, Ann Frances DeCiantis. The family lived in West Warwick, RI. Dorothy DeCiantis died in 1973 and Michael DeCiantis died in 1993.