The Guadalupe fur seal (GFS, Arctocephalus townsendi) was distributed on the islands of Baja California, Mexico, and southern California, United States. The species was intensively hunted during the 19th century, and in the late 1920s it was thought that it was extinct, but in 1954, a few animals were located on Isla Guadalupe, Baja California. Since the current status of the GFS population is unknown, we used counts of pups collected between 1984 and 2013 from Isla Guadalupe, which is still the only place where the species reproduces, and used Bayesian inference to assess both the population trend and abundance. The GFS population increased from 1984 to 2013 at an average annual growth rate of 5.9% (range 4.1–7.7%), and for 2013 the abundance was estimated between 34,000 and 44,000 individuals. The current abundance of the GFS represents about one-fifth of the estimated historical population size, and although the population has continued to increase, the species has not expanded its breeding range, which potentially affects its recovery.