Little is known about the frequency of ongoing HIV transmission within U.S. African immigrant communities. We used HIV surveillance and partner services data to describe African-born persons newly reported with HIV infection in King County (KC), WA from 1/1/2010 to 12/31/2013. We performed phylogenetic clustering analysis of HIV-1 pol to identify putative transmission events within this population. From 2010 to 2013, 1148 KC adults were reported with HIV, including 102 (9 %) born in Africa. Forty-one African-born cases were interviewed and reported diagnosis after arrival in the U.S. Fourteen (34 %) reported ≥1 negative test prior to diagnosis, and 9 (26 %) reported ≥1 negative test after U.S. arrival. Pol genotypes were available for seven of these nine. For two of these seven, a KC case was the nearest phylogenetic neighbor; two others were infected with subtype B virus. We found substantial evidence of ongoing HIV transmission in the African community of KC.