Brought up in Manchester, England, by Swiss parents, Bosshardt completed an apprenticeship as an engineer. He was accepted for training by the China Inland Mission (CIM) and in 1922 was appointed to western China, He worked in Kweichow (Guizhou) Province, which in 1924 was overtaken by famine and disease; he became engaged in relief work, and nearly died from typhus. In 1931 he married Rose Piaget, a Swiss CIM missionary.
In September 1934 the Bosshardts were among a missionary party abducted by a section of the Communist armies and held hostage for a huge ransom (described as a fine for spying). The women were soon released, but Bosshardt and a New Zealander, Arnolis Hayman, were taken by the Second Army on the epic Long March. Beatings and threats of execution heightened their sufferings. Their fate attracted attention in the West and, following the execution of John and Betty Stam, led to appeals for concerted prayer by the world Christian community. Hayman was released, but Bosshardt was held until Easter 1936, when he had covered more than 6,000 miles. His ability to translate French maps made him useful to his captors as a guide. When released, he was desperately ill and needed long convalescence. He returned to Kweichow in 1940, and when the Communist army reached Panhsien (Panxian) in 1950, he remained with the city's small church until the withdrawal of missionaries in 1951. The Bosshardts then shared in the expansion of CIM (renamed Overseas Missionary Fellowship) activity to Southeast Asia, working in Pakse, Laos, until Rose died in 1965. Alfred returned to Manchester, working with the Chinese church there until paralysis overtook him in 1990.
Bosshardt's book describing his captivity, The Restraining Hand (the title indicating the divine restraint on his captors), was reprinted several times. Three decades later with the help of ghost writers, he retold the story as The Guiding Hand, in the wider context of his life. A Chinese version bears a commendatory foreword by the Communist commander, Xiao Ke, the last surviving leader of the Long March, whom Bosshardt met again, in friendship, in the 1980s.