This study evaluated the toxicological effects of raw and cooked Mucuna pruriens seeds using its effect on liver enzymes and serum bilirubin (total and conjugated) of white albino Wistar rats in the laboratory. Powdered raw and cooked M. pruriens seed meal were incorporated into the feed of rats at different percent (10,20 and 50%) inclusion levels for the test animals while normal feed was given to the negative control rats for 28 days after which blood samples were collected from each rat for serum analysis. The tests conducted were serum Aspartate Amino Transaminase (AST), Alanine Amino Transaminase (ALT), Alkaline Phosphatase (ALP), Total bilirubin (TB) and Conjugated Bilirubin (CB). The liver function tests revealed that the serum AST, ALT, ALP as well as the total and conjugated bilirubin were significantly (P<0.03) increased in the rats that were fed 10 and 20% raw Mucuna seed meal in the feed and also significantly (P<0.0001) increased in the rat fed with 50% raw Mucuna in the feed when compared to the negative control. Also the liver enzymes and serum bilirubin (total and conjugated) of the rats that received different percent (10,20 and 50%) inclusion levels of cooked M. pruriens seed in the feed were significantly (P<0.05) increased when compared to the negative control group. In all the experiments, the level of the liver enzymes and serum bilirubin increased with increase in the percent level of inclusion in the feed. In conclusion this study suggested that M. pruriens may have hepatotoxic potentials which may be dose dependent and may be reduced by cooking the seeds before incorporation into the feed.