Petrochemical wastewaters have high ammonium contents that can cause serious environmental pollutions. Among different treatment methods, biological ammonia removal using bacteria has been attracted more attention due to their environmental friendly and high efficiency. The aim of the present study was to isolate heterotrophic nitrogen removal and aerobic denitrifying bacteria from petrochemical wastewater to be used for bioremediation. Wastewater and sludge samples were prepared and their chemical parameters were analyzed. Bacterial isolation was done through enrichment in mineral salt medium and basal salt medium and identified through 16S rRNA gene sequencing. The ability of isolates was evaluated at different concentrations of ammonia, nitrate, and carbon sources and at different time intervals. As a result, ten bacterial isolates were obtained that 5 strains were identified as heterotrophic nitrogen removal bacteria and 5 strains were able to do aerobic denitrification. From these, Pseudomonas guguanensis strain 4-n-1 with 93.2% ammonia removal during 24 h at 40 mg/L ammonium sulfate concentration and Pseudomonas guariconensis strain 5-d-1 with 89.2% denitrification during 24 h at 100 mg/L nitrate concentration were the best isolates. Finally, based on the efficiency of these isolates it can be concluded that effective ammonia removal can be achieved using these species as consortium and simultaneous heterotrophic nitrogen removal with aerobic denitrification is suitable method for efficient ammonium removal from petrochemical wastewater and reduction of ammonia concentration.