Upon retirement from the military, Rheault served as an instructor, program leader, and later, acting president of the Hurricane Island Outward Bound School in Rockland, Maine; retiring from the school in 2001 after 32 years of service. He also taught at the Northfield Mount Hermon School in Massachusetts. Rheault served on the board of directors of "The Apprenticeshop", a traditional boat building and maritime school in Rockland, as well as on the board of directors of "The Warrior Connection", a 501(c)(3) organization dedicated to the rehabilitation of military veterans suffering from posttraumatic stress disorder (PTSD). In 1947 Rheault married Caroline Young (1927–2006), a Vassar College student from New York, and they had three children: Susanne; Michèle; and Robert B. Rheault Jr. Like her husband, Caroline Young Rheault was fluent in French. She frequently traveled to and maintained a residence in France, and was an artist and book illustrator in Martha's Vineyard. Rheault resided in Owls Head, Maine, with his second wife, Susan St. John, married in 1977, and the couple adopted two children, Nicholas St. John-Rheault and Alexis St. John-Rheault. Rheault's son, Robert B. Rheault, Jr. (born 1958), is a marine biologist with a doctoral degree in biological oceanography from the University of Rhode Island who serves as the Executive Director of the East Coast Shellfish Growers Association. Rheault died on October 16, 2013, at his home in Owls Head, Maine. Rheault was interviewed for Ken Burns and Lynn Novick's PBS documentary series, "The Vietnam War", which aired in September 2017, four years after his death.