The present report aimed to describe the roles of ultrasonic power and reaction time in the Fenton reagent-based degradation of carbazole in wastewater, and to analyze the effects of the Fe2SO4 and H2O2 concentrations and the initial pH on the reaction kinetics. Application of 40 or 80 W of ultrasound at a frequency of 40 KHz substantially improved the effectiveness of carbazole degradation, whereas application of 20 W of ultrasound had little effect. The optimal concentration of the Fe2SO4·7H2O catalyst was lower for extended operating times. Increased degradation was observed with increasing H2O2 concentrations below 1.8 mg L−1, whereas decreased degradation was observed at concentrations above this value. The best performance was obtained at a neutral or slightly alkaline pH range (pH 7–9) rather than at the commonly used acidic pH range (pH 2–4). Under optimal conditions, the extent of carbazole degradation was 98% after 180 min. The degradation process followed second-order kinetics.