An experimental set‐up was used to evaluate Henry's constant (H) of H2S in distilled water and one of the sewage treatment plants in Kuwait. Calculated values of (H) for H2S in distilled water were found to agree with published works. For sewage, (H) was found to have a mean value of 601 atm/mole fraction for a temperature range of 20°C to 40°C. Factors affected the value of (H) in sewage were: initial concentration, flow rate of stripping fluid, pH, and pK. Effect of each factor was investigated and results were correlated.