Alexander George Findlay (the younger) was born in London on 6 January 1812. His father, also called Alexander Findlay, was an engraver and cartographic and hydographic publisher. As a child and young man Findlay the younger's interest in geography was encouraged and his training supervised by his father. In 1844 he was elected fellow of the Royal Geographical Society and he soon became an active member of its council and committees. In 1842 he published a revised version of Brookes's Gazetteer and The Coasts and Islands of the Pacific Ocean. The latter was the first of many meticulously compiled hydrographical works, with his Classical Atlas (1847) being the most widely circulated of his geographical works.

Findlay’s meteorological research attracted the attention of Admiral Fitzroy who invited him to join an official department of meteorology then being established, but Findlay preferred an independent career. On the death in 1858 of Richard Holmes Laurie, for whom he, like his father, had done much work, Alexander George Findlay took over that business and directed it to new success—it became one of the longest running hydrographic publishing houses in Europe. Between 1869 and 1875 Findlay prepared and published six navigational directories which in text, maps, and diagrams documented the winds, currents, coastlines, and other information necessary for navigation in the major oceans of the world. His interest in lighthouses won him a medal from the Society of Arts and led to the publication of various editions of A Description and List of Lighthouses of the World.

Findlay kept up his geographical work and took a keen interest in exploration. As a member of the Arctic committee of the Royal Geographical Society he helped to analyse possible routes taken by Sir John Franklin and gave valuable help in preparing the case which persuaded the government to send out the Alert and Discovery expedition in 1875. He was also active in mapping the discoveries being made in Africa and the quest for the source of the Nile. He was a friend of David Livingstone. He worked actively for the British Association for the Advancement of Science and gave papers on ocean currents and climatology to its conferences in 1853 and 1869 respectively. He married his wife Sarah Rutley on 15 October 1850. Their marriage appears to have been childless.

In 1870 the Società Geographica Italiana elected Findlay to foreign honorary membership in recognition of his services to hydrography and geography. He received the medal of the Congrès International des Sciences Géographiques in Paris in 1875. Many of his numerous maps, charts, and scientific papers remained in use long after his death, of heart disease, on 3 May 1875 at 1 Sydney Villas, Dover, where he was visiting from his home at Dulwich Wood, London.