Chromolaena odorata (L.) R.M. King and H. Robinson (Asteraceae) is one of the worst invasive weeds in Africa, Asia, and the Pacific. Cecidochares connexa (Macquart) (Diptera: Tephritiidae) is a biological control agent of C. odorata. It was introduced into Côte d'Ivoire in 2003 and spread across West Africa. This paper reports the establishment, distribution, and density of C. connexa in Nigeria, the seventh country in West Africa with a confirmed report of C. connexa. It is anticipated that the gall fly, recorded in Nigeria, will have similar impacts on C. odorata as in the other six countries. [ABSTRACT FROM AUTHOR]