Beardsley was born in Brighton on 21 August 1872. His father, Vincent Paul Beardsley (1839 – 1909), was the son of a tradesman; Vincent had no trade himself, however, and instead relied on a private income from an inheritance that he received from his maternal grandfather when he was twenty-one. Vincent's wife, Ellen Agnus Pitt (1846 – 1932), was the daughter of Surgeon - Major William Pitt of the Indian Army. The Pitts were a well established and respected family in Brighton, and it is widely accepted that Beardsley's mother married beneath her station. Shortly after their wedding, Vincent was obliged to sell some of his property in order to settle a claim for "breach of promise" from another woman who claimed that he had undertaken to marry her. At the time of his birth, Beardsley's family, which included his sister Mabel who was one year older, were living in Ellen's familial home at 12 Buckingham Road.

In 1883 his family settled in London, and in the following year he appeared in public as an "infant musical phenomenon," playing at several concerts with his sister. He attended Brighton, Hove and Sussex Grammar School in 1884, before moving on to attend Bristol Grammar School, where in 1885 he wrote a play, which he performed together with other students. At about the same time his first drawings and cartoons were published in the school newspaper of the Bristol Grammar School Past and Present. In 1888 he obtained a post in an architect's office, and afterwards one in the Guardian Life and Fire Insurance Company. In 1891, under the advice of Sir Edward Burne - Jones and Pierre Puvis de Chavannes, he took up art as a profession. In 1892 he attended the classes at the Westminster School of Art, then under Professor Fred Brown.

His six years of major creative output can be divided into several periods, identified by the form of his signature. In the early period his work is mostly unsigned. During 1891 and 1892 he progressed to using his initials - A.V.B. In mid 1892, the period of Morte D'Arthur and The Bon Mots he used a Japanese influenced mark which became progressively more graceful, sometimes accompanied by A.B. in block capitals. He co-founded The Yellow Book with American writer Henry Harland, and for the first four editions he served as art editor and produced the cover designs and many illustrations for the magazine. He was also closely aligned with Aestheticism, the British counterpart of Decadence and Symbolism. Most of his images are done in ink, and feature large dark areas contrasted with large blank ones, and areas of fine detail contrasted with areas with none at all.

Beardsley was the most controversial artist of the Art Nouveau era, renowned for his dark and perverse images and the grotesque erotica, which were the main themes of his later work. Some of his drawings, inspired by Japanese shunga, featured enormous genitalia. His most famous erotic illustrations were on themes of history and mythology; these include his illustrations for a privately printed edition of Aristophanes' Lysistrata, and his drawings for Oscar Wilde's play Salome, which eventually premiered in Paris in 1896.

He also produced extensive illustrations for books and magazines (e.g. for a deluxe edition of Sir Thomas Malory's Le Morte d'Arthur) and worked for magazines such as The Studio and The Savoy, of which he was a co-founder. Beardsley also wrote Under the Hill, an unfinished erotic tale based loosely on the legend of Tannhäuser, published in The Savoy. Beardsley was a caricaturist and did some political cartoons, mirroring Wilde's irreverent wit in art. Beardsley's work reflected the decadence of his era and his influence was enormous, clearly visible in the work of the French Symbolists, the Poster art Movement of the 1890s and the work of many later period Art Nouveau artists like Pape and Clarke.

Beardsley was a public character as well as a private eccentric. He said, "I have one aim — the grotesque. If I am not grotesque I am nothing." Wilde said he had "a face like a silver hatchet, and grass green hair." Beardsley was meticulous about his attire: dove - grey suits, hats, ties; yellow gloves. He would appear at his publisher's in a morning coat and patent leather pumps.

Although Beardsley was aligned with the homosexual clique that included Oscar Wilde and other English aesthetes, the details of his sexuality remain in question. He was generally regarded as asexual — which is hardly surprising, considering his chronic illness and his devotion to his work. Speculation about his sexuality include rumors of an incestuous relationship with his elder sister, Mabel, who may have become pregnant by her brother and miscarried. Through his entire career, Beardsley had recurrent attacks of the disease that would end it. He suffered frequent lung hemorrhages and was often unable to work or leave his home.

Beardsley converted to Catholicism in March 1897, and would subsequently beg his publisher, Leonard Smithers, to “destroy all copies of Lysistrata and bad drawings... by all that is holy all obscene drawings." Smithers ignored Beardsley’s wishes, and actually continued to sell reproductions as well as forgeries of Beardsley's work.

Beardsley was active till his death in Menton, France, at the age of 25 on 16 March 1898 of tuberculosis.