Coastal lowlands of extreme southern Somalia (Boni Forest), Kenya (inland along river valleys to Garissa, southern Tsavo East National Park, southern Tsavo West National Park and L Jipe) and northern Tanzania (L Jipe east to northern Pare Mts, and at coast from Tanga south to Zanzibar, inland to eastern Usambara Mts and Uluguru Mts).
 
Population
Estimated population is unknown (2011).
East Coast Boubou (Laniarius sublacteus) [XC456803]
by Frank Lambert from Arabuko-Sokoke Forest, Kenya (song)
East Coast Boubou (Laniarius sublacteus) [XC33824]
by James and David Bradley from Tent with a view' lodge, Saadani, Tanzania (duet, song)
Subspecies
No subspecies.
Laniarius liberatus (Sibley and Monroe 1990, 1993; Dowsett and Forbes-Watson 1993) is now treated as a synonym of erlangeri of Ethiopian Boubou (Laniarius aethiopicus) following Nguembock et al. (2008) who also recommend splitting Laniarius aethiopicus into Ethiopian Boubou (Laniarius aethiopicus), Manda Boubou (Laniarius nigerrimus), Zanzibar Boubou (Laniarius sublacteus) and Tropical Boubou (Laniarius major), proposals that are currently under review by the BirdLife Taxonomic Working Group.
Formerly, was widely treated as a subspecies of Ethiopian Boubou (Laniarius aethiopicus). However, recent molecular-genetic studies indicate closer relationship with Southern Boubou (Laniarius ferrugineus), to the extent that the two can be regarded as a forming superspecies.