Born in Chester, England, Hugh B. Cave relocated during his childhood with his family to Boston, Massachusetts, soon after the beginning of World War I. His first name was in honor of Hugh Walpole, a favorite author of his mother, a nurse, who had once known Rudyard Kipling.
Cave attended Brookline High School. After graduating, Cave attended Boston University on a scholarship but had to leave when his father was severely injured. He worked initially for a self-publishing press, the only regular job he would ever have. He quit this position at age 20 to write for a living.
From 1932 until his death in 1997, Cave corresponded extensively with fellow pulp writer Carl Richard Jacobi. Selections of this correspondence can be found in Cave's memoir Magazines I Remember. During the 1930s, Cave lived in Pawtuxet, Rhode Island, but he never met H.P. Lovecraft, who lived in nearby Providence. The two engaged in a debate by correspondence (non-extant) regarding the ethics and aesthetics of writing for the pulp magazines. At least two of Cave's stories are associated with Lovecraft's Cthulhu Mythos – "The Isle of Dark Magic" and "The Death Watch".
During World War II Cave travelled as a reporter around the Pacific Ocean area and in Southeast Asia. Soon after the war he relocated to the Caribbean area, spending five years in Haiti, after which he rebuilt and managed a successful coffee plantation in Jamaica. He returned to the United States during the early 1970s after the Jamaican government confiscated his plantation.
Hugh Cave was married twice, first to Margaret Long in a union that produced two sons before the couple began living apart, and to Peggy (or Peggie) Thompson, who died during 2001.
Cave was 93 when he died in Vero Beach, Florida on 27 June 2004. His remains were cremated.