Expectant and lactating mothers resort to medicinal plants for it claimed nutritional values, such practices effects on offspring neurodevelopment and cognitive functions are unclear. Hence, this study assessed cognitive function and hippocampus in juvenile rat exposed to aqueous leaf extract of Jatropha tanjorensis (ALEJT) in-utero and postnatal life. Thirty litters were randomly assigned 3 groups (n=10) following dams intake. Control: 20ml/kg of distilled water; In-utero and In-utero+postnatal days 15-21 ALEJT 500mg/kg oral exposure respectively. Cognitive assay after weaning: Novel object recognition task (NORT); Morris water maze (MWM) and T maze; Histological studies: hematoxylin and eosin staining. NORT short term memory; exposed groups index of habituation increased against control. Index of discrimination differed not. Long term memory: Group 3 index of habituation increased (p<0.05) against control, and was positive against other Groups. Exposed groups index of discrimination was negative against control. Group 2 (p<0.05) reduced against control. During MWM acquisition training, day 3 swim latency (SL) was shorter in Group 3 (p< 0.01) against control. During reversal training, day 1 SL was shorter in Group 3 against control (p<0.05) and Group 2 (p<0.01); shorter on day 2 (p<0.05) against Group 2 and on day 3 (p<0.01) against control. During probe trial Group 3 spent time in Northwest quadrant against the retention quadrant (Southwest). Group 3 SL during visible platform was shorter (P<0.01) against control. Percentage alternation differed not. Exposed rats hippocampus showed altered pyramidal cells, with reactive astrocytes present. ALEJT impairs cognitive function with potential injuries to hippocampus of exposed rats.