First studied art in the school of art at Manchester. Subsequently he came to London and was admitted to the schools of the Royal Academy. In 1855, he exhibited for the first time at the Royal Academy, sending ‘An Ancient Mariner.’ He became chiefly known as a successful portrait-painter, and gained frequent commissions for official and presentation portraits.

Among these were portraits of Professor Fawcett, Bishop Colenso, Lady Brassey, the Duke and Duchess of Buckingham. He also painted some subject pictures, of which ‘Alice in Wonderland,’ ‘The Challenge,’ and a few others, were engraved and met with some popularity. Sidley continued to paint up to the time of his death, which took place at 8 Victoria Road, Kensington. He was a member of the Royal Society of British Artists, and an original associate of the Royal Cambrian Academy.