This study assesses the hematological and histopathological effects of some identified piscicidal plants on post-juvenile Clarias gariepinus. ^1/10LC₅₀ values of each of the five aqueous extracts and ammonium solution were used for the 28-day sub-acute test. The fishes were exposed for 14 and 28 days and on the 28^th day, the group was allowed to recover. and  RBC, WBC, as well as PCV were estimated using electronic counters. The activities of the liver enzymes; ALT, AST, and ALP were determined for exposure and recovery. Gill and liver alterations after exposure were estimated for each of the extracts. There was a decrease in RBC and PVC from the 14^th day and 28^th day exposure in all the extracts. A. occidentale had the lowest RBC level after 28 days of exposure. ALT increased after recovery for all the extract except for N. tabacum. ALP increased after recovery only for A. occidentale. A. occidentale and N. tabacum showed the highest liver and gill alterations with high frequencies of severe vacuolization, inflammation, degeneration, and necrosis with alteration index of 2.44 and 3.33 respectively.