Histological studies on rats fed with Aspergillus niger fermented Chrysophyllum albidum seed meal based diet was carried out in selected tissues of weaned male albino rats. Eighteen wean male albino rats were randomly distributed into 3 groups with each treatment consisting of 6 rats. The 1st group was placed on soya bean meal based diet, this served as the control group, the 2nd group on raw Chrysophyllum albidum seed meal based diet and the 3rd on fermented Chrysophyllum albidum seed meal based diet for 3 weeks. Average weekly weight gain of rats fed on soya bean meal based diet (SM) WAS 39±6.84, 1.46±0.48, for rats fed on Chrysophyllum albidum seed meal based diet (RWA) and 3.67±1.20 for rats fed with the experimental diet (FCA). Histologically, rats fed on RCA diet showed complete distortion of stomach architecture and pronounced areas of haemorrhage in the liver, which are indicative of inflammatory changes in the liver, whereas these degenerative effects were not seen in rats fed on FCA diet. It may therefore be inferred that fermentation improved the quality of Chrysophyllum albidum seed meal based diet, reduced level of antinutrient in the feed and consequently enhanced the weight of animals fed on Aspergillus nigeChrysophyllum albidum seed meal based diet over those fed on the RCA diet as evidenced in the rat tissues.