Born in London, Behnes was the son of a Hanoverian pianoforte-maker and his English wife. His brother was Henry Behnes, also a sculptor, albeit an inferior one. His early life was spent in Dublin where he studied art at the Dublin Academy.
After the family returned to London, Behnes continued his artistic training, studying at the Royal Academy School of Art from 1813. As a painter, he exhibited at the Royal Academy in 1815 and won several medals during the ensuing years. In 1819 he won a Society of Arts gold medal for inventing an instrument to assist sculpture work, having by this time begun to practice successfully as a sculptor.
In 1837 Behnes was appointed 'Sculptor in Ordinary' to Queen Victoria. His pupils included noted sculptors George Frederic Watts, Thomas Woolner and Henry Weekes, and naturalist Benjamin Waterhouse Hawkins.
He produced many busts of children, reliefs and also some notable church monuments and statues, including ones of Dr William Babington in St Paul's Cathedral and Major-General Sir Henry Havelock (believed to be the first statue based on a photograph, two casts were made - one is today situated in Trafalgar Square, London, the other in Mowbray Park, Sunderland) and several of Sir Robert Peel (including ones situated in Leeds, Peel Park in Bradford, and at the police college in Hendon in north-west London). Other subjects included: Thomas Arnold, Sir Joshua Reynolds, Benjamin West and George Cruikshank.
Despite this success, he was financially inept and was declared bankrupt in 1861, and died in poverty.
- Mapping the Practice and Profession of Sculpture in Britain and Ireland 1851-1951
- "Stevens T. 'Weekes, Henry (1807–1877)', Oxford Dictionary of National Biography (2004)". Oxford University Press. Retrieved 2008-03-17.