Alfred Sharpe was baptised on 30 September 1836 at Tranmere, near Birkenhead, Cheshire, England. He was the second child of Liverpool merchant William Sharp and his wife, Mary Edwards. His father was a collector of paintings and took young Alfred to visit exhibitions and private collections. By his own account, Alfred studied at the Birkenhead School of Arts, and spent two years in the west of Ireland before emigrating to New Zealand.
Alfred Sharp arrived at Auckland on the Tornado on 26 September 1859, and the published passenger list reveals that he had already decided to add the more distinguished final 'e' to his family name. For the first six years Sharpe was a settler on the Mata Creek estuary near Mangapai, south of Whangarei. On 3 April 1865 he received a Crown grant of 38 acres there, but by early 1866 he had mortgaged his land and moved to Auckland. There, on 25 July 1866, he married Jane Jeffares, originally of County Wexford, Ireland; the couple were to have no children. They settled in Auckland. Sharpe relinquished his Mata Creek property.
During the 1870s Alfred Sharpe exhibited large-scale watercolours with the newly founded Auckland Society of Artists and at venues in Wellington, Sydney and Melbourne, as well as in Auckland shop windows. Later in the decade he organised solo exhibitions in the form of art unions, or raffles. While he regarded himself as a professional artist, the paintings were produced in the time allowed by a full-time position as an architectural draughtsman and part-time art teaching.
Sharpe produced probably between 100 and 150 paintings in New Zealand, of which fewer than 100 have survived. Unlike New Zealand contemporaries such as John Gully and J. B. C. Hoyte, he rarely repeated his compositions. Geographically the works range from the Bay of Islands to Waikato and the Coromandel Peninsula, concentrating on sites within easy reach of Auckland. In style they owe much to the Pre-Raphaelite landscapes the artist had seen in Liverpool in the 1850s, incorporating high viewpoints, sharp focus and vivid colour. They also represent a highly sophisticated adaptation of Victorian watercolour technique, derived in part from Sharpe's library of practical manuals by Aaron Penley, T. L. and T. C. L. Rowbotham and others.
Although he became profoundly deaf, Sharpe was never the deaf-mute of persistent local tradition. He did, however, have deaf friends and learned the manual sign language. He used an interpreter in the deaf-and-dumb alphabet when he was charged in January 1880 with assaulting a female servant (he was convicted and fined for the offence). His wife Jane was an invalid, reportedly an alcoholic and hypochondriac. Increasingly, Sharpe took up writing as a creative outlet. In the series of essays entitled 'Hints for landscape students in water-colour' (1880–82) he claimed to present advice 'entirely from a New Zealand standpoint, especially so as our scenery and atmosphere are sui generis'. These writings establish Sharpe as New Zealand's leading art theorist of the nineteenth century, and also provide an unparalleled commentary on the working procedures behind some of the period's most original landscape watercolours.
In addition to these signed writings, Sharpe published a significant number of pseudonymous articles under names like 'Asmodeus', 'Censor' and 'Conservator'. These addressed wider issues such as arboriculture, acclimatisation of vermin, political corruption and a host of other topics. Consisting of over 100 lengthy essays, Asmodeus's writings represent a cathartic outpouring which appeared in Auckland newspapers such as the New Zealand Herald, National Punch and the Observer and Free Lance. An early series is 'The ethnologic aspect of Auckland', in which he rants against the 'Muddleheads' (the Auckland Domain Board, Auckland Acclimatisation Society), the 'Unmitigated Cusses' (butchers and bakers, brothel-keepers, hobbledehoys and slubberdegullions) and the 'Iconoclasts' (land sharks, arboricides, evangelists, feminists), as well as other 'races'. Cantankerous and chauvinistic, the writings of Asmodeus provide a fascinating insight into the mind of Alfred Sharpe, and also help to explain his isolation from Auckland's cultural élite.
Sharpe's distinctive style of painting was recognised in his own time, although some critics disapproved. As with the work of Dunedin contemporary George O'Brien, his detailed watercolours were dismissed as 'painfully elaborate', 'harsh' and 'photographic'. Unlike O'Brien, however, he defended his work in published letters which outline his aesthetic credo, and reveal a keen awareness of posterity and his work's importance. Sharpe continued to exhibit throughout the 1880s with the reformed Auckland Society of Arts, and he was a leading member of a rival group, the New Zealand Art Students' Association from 1884 to 1887. This group's call for specific New Zealand content fitted perfectly with Sharpe's documentary approach.
Late in 1887 Sharpe moved to Newcastle, New South Wales, where his younger brother, William Bethal Sharp, was a prominent citizen. He thereby abandoned his wife, although he paid for her upkeep in the Auckland old people's refuge until her death there on 2 May 1888. In Newcastle Asmodeus wasted little time in denouncing the city's lack of civilised amenities such as trees, parks and modern sewage disposal, while Sharpe republished the 'Hints' and other writings under his own name (from which he had now dropped the 'e').
Although Sharpe does not enjoy an Australian reputation comparable to his standing in New Zealand art history, he made a significant contribution during his two decades' residence in Newcastle. He designed the city's principal parks (importing a large number of pohutukawa) and practised as an architect. He continued to paint landscapes in watercolour, exhibiting them at agricultural shows and music festivals, and produced over 50 large illuminated addresses commissioned for special presentations. He died on 12 December 1908 at Newcastle, where he is buried in an unmarked grave in Sandgate cemetery. Most of Sharpe's paintings are in private hands and in the Auckland City Art Gallery. The principal Australian collection is in the Mitchell Library, Sydney.