Mixed microbial culture collected from the wastewater treatment plant of Indian Institute of Technology Guwahati (IITG) was further grown in anaerobic condition in presence of sulfate where lactate was added as a carbon source. Sulfate addition was increased stepwise up to 1,000 mg l−1 before phenol was added at increasing concentrations from 10 mg l−1 to 300 mg l−1. Kinetics of sulfate, phenol and chemical oxygen demand reduction were studied and experimental findings were analyzed using various bio-models to estimate the bio-kinetic coefficients. This is the first detailed report on kinetics and bio-kinetic studies of sulfate reduction in presence of phenol. Experimental results showed that there was no inhibition of sulfate reduction and microbial growth up to 100 mg l−1 phenol addition. However, inhibition to different degrees was observed at higher phenol addition. The experimental data of microbial growth and substrate consumption in presence of phenol fitted well to the Edward model (R2 = 0.85, root mean square error = 0.001011) with maximum specific growth rate = 0.052 h−1, substrate inhibition constant = 88.05 mg l−1 and half saturation constant = 58.22 mg l−1. The characteristics of the cultured microbes were determined through a series of analysis and microbial tests.