Study of the length - weight relationship (LWR) and condition factor (K) of African mud fish in Lapai - Agaie Reservoir, Niger State was carried out between April 2018 - July, 2018. Two hundred and fifty one (251) samples were collected from fishermen catches and used for this study. This comprises 0f one hundred and ten (110) males and one hundred and forty one (141) females. There were variations in the standard length, total length and weight of males and females, which were not significantly different (P>0.05) from each other. Females were bigger than males, although smaller in size compared to other water bodies within the zone. The parameter "b" that describe growth pattern was obtained from the linear regression of the growth equation, W = aLb when transformed to log length and log weight of fish respectively. The b values of C. gariepinus for male (2.8), female (2.39) and pooled (2.56) indicated negative allometric growth pattern , which implies that the length and weight of fish did not grow at the same proportion. Condition factor (K) of male (0.75±0.18) revealed that the environment is not conducive for the survival of the fish. It is recommended therefore, that there is need to carryout similar study for the month of the year, other aspects of the biology should be studied, water quality parameters of the reservoir assessed and catching of C. gariepinius at this period should also be discouraged