He devoted himself to glass engraving, on goblets and bowls blown to his own designs, and (increasingly, as he became more celebrated) on large-scale panels and windows in churches and private houses. He also engraved on three-sided prisms, some of them designed to revolve on a small turntable so that the prism's internal reflections complete the image. The best-known of these was done as a memorial to his elder brother, Rex Whistler. His son, Simon Whistler, also became a glass engraver. In 1935 Laurence Whistler became the first recipient of the King's Gold Medal for Poetry. However, he largely turned away from verse to concentrate on glass engraving.
His early works include a casket for the Queen Mother, and a hinged glass triptych to hold her daily schedule. Other engravings of his can be found, for example, in Salisbury, where his family lived during part of his childhood, including a pair of memorial panels with quotations by T. S. Eliot, and the Rex Prism in the Morning Chapel, both in Salisbury Cathedral; at the Ashmolean Museum; at Balliol College, Oxford where he was an undergraduate, and St Hugh's College, Oxford, where he also designed the Swan Gates leading from the college grounds onto Canterbury Road; at Stowe House in Stowe, Buckinghamshire; at the village church of St Nicholas at Moreton, Dorset, where every single window was engraved by him over about 30 years; and in the Corning Museum of Glass (USA).
In 1947, Whistler created one of the wedding gifts for Princess Elizabeth, a glass goblet engraved with the words of a 1613 poem by Thomas Campion, written for the marriage of Elizabeth of Bohemia, daughter of James I. 
In 1975 he became the first President of the newly founded British Guild of Glass Engravers.
In 1939 Laurence Whistler married actress Jill Furse (died 1944); they had two children, Simon Whistler and Caroline (Robin) Whistler. In 1950 Laurence Whistler married Jill Furse's younger sister, Theresa (1927–2007), but the marriage was later dissolved. They had another two children Daniel and Frances. In 1987 he married a third time, but was divorced in 1991.
- Oxford Dictionary of National Biography, Whistler, Sir (Alan Charles) Laurence (1912–2000), glass engraver, writer, and architectural historian, by Robin Ravilious
- The Initials in the Heart. Michael Russell Publishing Ltd. (June 2000) ISBN 0-85955-257-8
- Point Engraving on Glass (The Decorative Arts Library). Walker Books Ltd. (September 1997), ISBN 0-7445-1894-6
- The Laughter and the Urn: The Life of Rex Whistler. Weidenfeld & Nicolson Ltd (January 1986) ISBN 0-297-78603-2
- The Image on the Glass. Cupid Press (1975), ISBN 0-7195-3275-2
- Stowe: Guide to the Gardens. E. N. Hillier & Sons, 3rd (further revised) edition (January 1, 1974)