Hartlaub was born in Bremen, and studied at Bonn and Berlin before graduating in medicine at Göttingen. In 1840, he began to study and collect exotic birds, which he donated to the Bremen Natural History Museum. He described some of these species for the first time. In 1852, he set up a new journal with Jean Cabanis, the Journal für Ornithologie.

A number of birds were named for him, including Hartlaub's Bustard, Hartlaub's Duck, and Hartlaub's Gull.