Richard was the only son of William Crashaw, a puritan preacher in London who had officiated at the burning of Mary, Queen of Scots. In defiance of his father's views on religion, Crashaw went to a High Church college at Cambridge, Pembroke. He later became a fellow of Peterhouse College but was forced to resign because of his Roman Catholic leanings.

Victory for Oliver Cromwell's Puritans in the Civil War made England a dangerous place for Catholic sympathisers like Crashaw, and in 1644 he fled to France. He became a Catholic sometime around 1645. His friend Abraham Cowley found him living in poverty in Paris, and introduced him to Charles I's Queen, Henrietta Maria. She sent Crashaw to Rome with a recommendation to the Pope. On his arrival in Italy however, Crashaw was simply allotted a position in a cardinal's household. Four months before he died, he was made a sub-canon of the Cathedral of Santa Casa in Loreto.

Crashaw was much influenced by the Italian poet Marino, as well as his reading of the Italian and Spanish mystics. Though his verse is somewhat uneven in quality, at its best it is characterised by brilliant use of extravagant baroque imagery.