After two years at the Roman College he was made professor of moral philosophy and controversy at the Jesuit College of Dillingen in Bavaria where he stayed for seventeen years. In 1570 he took the full Jesuit vows. In 1581 he came to England as a missionary with Father William Holt, and together they were the means of numerous conversions to the Catholic Faith. Father Heywood was appointed superior of the English Mission in succession to Father Parsons. In the controversy then rife concerning the observance by English Catholics of the severe ancient fasts, Heywood opposed the rigid party. He was considered by the authorities to have erred on the side of laxity, and was therefore recalled from England by his superiors. On this return journey he was arrested as a suspected priest, brought back to London and imprisoned. Several times he was examined by the Privy Council and strongly urged to conform, but neither bribes nor threats moved him, and he was brought up for trial at Westminster with other priests. Before the trial finished, however, he was taken to the Tower and closely imprisoned for seventeen months. Finally, he was exiled with others to the coast of France, and forbidden under pain of death to return. He then went to the Jesuit College at Dôle in Burgundy, and in 1589 was sent to Rome and afterwards to Naples, where, worn out by the sufferings and hardships he had undergone, he died at the age of sixty-three.
As a classical scholar he is known for his translations of three of Seneca's tragedies: the Troas the Thyestes and Hercules Furens.
John Donne's mother Elizabeth was Jasper Heywood's sister--and their father was the famous poet, playwright, and epigrammist, John Heywood. The Heywood and Donne families were devout Catholics, but John Donne left the Catholic Church soon after his brother Henry died in prison after being tortured and betraying Blessed William Harrison, SJ, who was executed on February 18, 1594. John Donne would also go on to write anti-Jesuit works: Ignatius His Conclave and the Pseudo-Martyr. Dennis Flynn explored John Donne's Catholic connections, including to his uncle in John Donne & The Ancient Catholic Nobility.