This work reports on ichthyotoxic effect of ethanol and aqueous extracts of Ageratum conyzoides leaf on Clarias gariepinus fingerlings. The investigation was carried out for 96h. The present work shows that the ethanol extract is more toxic to the fishes than the aqueous extract. The fishes showed pathological changes like moribund behavior, de-pigmentation and erratic swimming before death. The LC50 for the ethanol and aqueous extracts were observed at 5.3 and 8mgdm-3 respectively. No pathological changes were observed in the control. Ageratum conyzoides leaf is therefore unsuitable for in cooperation into fish feed.