This study adopted an ecosystem services approach to pollution management by investigating the impact of biochar-mediated remediation on soil nitrogen, abundance of nitrogen cycling bacteria and the activity of ammonia monooxygenase (AMO) enzyme in petroleum-polluted soil using two biochar types applied at two treatment levels with monitoring over 15 weeks. The corn cob-derived biochar (CDB), generally, had a stronger restorative effect on soil ammonium nitrogen, nitrate and total organic nitrogen concentrations than the bone-derived biochar (BDB). Both biochar types had a more robust impact on restoration of Nitrosomonas, Nitrobacter and Azotobacter abundance (with the re-establishment of pre-pollution levels) than on Rhizobium and Pseudomonas aeruginosa. Biochar amendment restored the activity of AMO enzyme in the soil by week 15. The CDB (72.4% – 73.7%) showed more effective total petroleum hydrocarbon (TPH) elimination capacity than the BDB (51.1% – 57.7%). Biochar amendments exhibited great potential for restoration of nitrogen cycling while facilitating remediation of petroleum-polluted soils.