Widespread deforestation has resulted in soil degradation that is often linked to environmental and ecological changes. Rehabilitation of degraded forest is essential to prevent further degradation of the soil. Abundance of soil microbiota could serve as an essential biological indicator of soil health for rehabilitation success. An investigation was conducted to study the relationship between cellulolytic, nitrogen-fixing and phosphate-solubilizing microbial counts and age of rehabilitated forest. A random sampling design was used to obtain four replicates of five composite soil of 0–10 cm depth soil samples of 4, 9, 14 and 19-year-old rehabilitated forest. Three selective media: Congo red cellulose, nitrogen-free malate and calcium phosphate media were used for the enumerations of cellulolytic, nitrogen-fixing and phosphate-solubilizing microbes, respectively. Cellulolytic and phosphate-solubilizing microbes were counted based on the formation of clearing zones, while nitrogen-fixing microbes were based on the formation of blue halo on the respective media. There was positive linear relationship between age of the rehabilitated forest and microbial count. These findings revealed that the potentials of cellulolytic, nitrogen-fixing and phosphate-solubilizing microbial populations could be used as biological indicators of forest soil rehabilitation.