To evaluate its importance as a possible reservoir host of tephritid pests (Diptera) of cultivated fruit, we sampled fruit of the exotic invasive Solanum mauritianum Scop. in various sites throughout its range in central and western Kenya. Tephritids were reared from S. mauritianum wherever the plant was found, except at the highest altitudes (2,200–2,500 m). Ceratitis anonae Graham and Ceratitis fasciventris (Bezzi) were reared from fruit sampled in western Kenya, whereas the latter and Ceratitis rosa Karsch were reared from fruit found in central Kenya. In Kakamega Forest in western Kenya, C. anonae was reared from S. mauritianum year-round, whereas C. fasciventris was present in only 52.6% of the collections at this locality. A host shift by C. fasciventris onto S. mauritianum during the drier months from November to January is suggested as an explanation for the observed change in relative rates of infestation of S. mauritianum by the two Ceratitis species in western Kenya. In Nairobi (central Kenya), C. fasciventris was reared from fruit collected year-round. C. rosa was not recovered until the last of 17 Nairobi collections. In Kenya, S. mauritianum maintains year-round populations of tephritid pests available to attack cultivated fruit. S. mauritianum should be considered a noxious invasive pest in Kenya, and efforts to eradicate or control it should be made wherever it occurs.