Oldfield recorded the double album Incantations between December 1977 and September 1978. This introduced more diverse choral performances from Sally Oldfield, Maddy Prior, and the Queen's College Girls Choir. When it was released on 1 December 1978, the album went to No. 14 in the UK and reached platinum certification for 300,000 copies sold.
In June 1978, during the recording of Incantations, Oldfield and his siblings completed a three-day Exegesis seminar, a controversial self-assertiveness program based on Werner Erhard's EST training program. The experience had a significant effect on Oldfield's personality, who recalled that he underwent a "rebirth experience" by reliving past fears. "It was like opening some huge cathedral doors and facing the monster, and I saw that the monster was myself as a newborn infant, because I'd started life in a panic." Following the Exegesis seminar, the formerly reclusive Oldfield granted press interviews, posed nude for a promotional photo shoot for Incantations, and went drinking with news reporters. He had also conquered his fear of flying, gained a pilot's license, and bought his own plane.
Oldfield has been married three times and has seven children. In 1978 he married Diana Fuller, a relative of the Exegesis group leader, which lasted for three months. Oldfield recalled that he phoned Branson the day after the ceremony and said he had made a mistake. From 1979 to 1986, Oldfield was married to Sally Cooper, who he met through Virgin. They had three children, daughter Molly and sons Dougal (1981–2015) and Luke. Shortly before Luke's birth in 1986, the relationship had broken down and they amicably split. By this time, Oldfield had entered a relationship with Norwegian singer Anita Hegerland, lasting until 1991. The pair had met backstage at one of Oldfield's gigs while touring Germany in 1984. They lived in Switzerland, France, and England. They have two children: Greta and Noah. In the late 1990s, Oldfield posted in a lonely hearts column in a local Ibiza newspaper. It was answered by Amy Lauer and the pair dated, but the relationship was troubled by Oldfield's bouts of alcohol and substance abuse and it ended after two months. In 2001, Oldfield began counselling and psychotherapy. Between 2002 and 2013, Oldfield was married to Fanny Vandekerckhove, who he had met while living in Ibiza. They have two sons, Jake and Eugene.