Abstract: The abundance and species diversity of mesofauna were surveyed in the unpolluted site, remediated site and crude oil polluted sites to examine the effect of crude oil on the abundance and diversity of mesofauna. The samples were collected on a line transect. Soil samples were collected and taken to the laboratory to isolate and identifymesofauna found in the soil samples. The pH, moisture content and moisture content of the soil samples were also obtained, where the unpolluted site has the highest pH followed by remediated site while the crude oil polluted site recorded the least pH. During the research work 37 individuals of mesofauna were encountered (distributed in 15 species) in the entire studied sites. Mesofauna abundance was highest in the unpolluted site (31 individuals) followed by the remediated site (4) while crude oil polluted site recorded the least abundance (2 individuals). Highest species diversity of mesofauna was also recorded in the unpolluted site (11). The results further explained that the effect of crude oil is significant (P≥0.05) on the abundance of mesofauna). The relationship between pH and mesofauna abundance and diversity showed that there were no significant differences (P<0.05). It was further observed that the pH of the unpolluted site with the mean value of 6.79 is higher than those of remediated (6.33) and crude oil polluted site (6.12). This work showed that abundance and species diversity of mesofauna in the study habitats were significantly different. Soil moisture content of the polluted site (32.29%) is higher than those of remediated (20.17%) and unpolluted site (20.32%). Soil temperature in the remediated site is the highest value (31.03°C) followed by the unpolluted site (29.14°C) while the crude oil affected site recorded the least temperature value (23.11°C).