<p>In the study synergic impacts of two amendments included biochar and iron nanoparticles were assessed to monitor the natural polluted soil by gasoil. Contaminated soil samples were collected in a polluted site in southern Iran by gasoil about 3 mg kg⁻¹ of soil. Soil samples were treated with 0, 1, 5 and 10% by weight of biochar and 0, 2 and 10 g kg⁻¹ synthetized iron nanoparticles under the incubation at 28 ± 2 °C and 70% field capacity moisture for 35 days. According to the results, the first order kinetic model fitted well with an R² value of 0.934–0.98 for the soils treated with different levels of biochar and nanoparticles. A significant and positive correlation (r = 0.774, <i>P</i> &lt; 0.01) derived from a polynomial equation was observed between cumulative respiration rate and change percentage of gasoil during biodegradation (ΔTPH). Increasing of biodegradation because of higher biochar is mainly related to improvement of circumstance for higher microbial activity, while inhibition effects of iron nanoparticles on decreasing microbial activities in 10 g kg⁻¹ is related to toxicity of nanoparticles on microbes. After 35 days of incubation, the highest ΔTPH was observed for 10% biochar and 2 g kg⁻¹ iron nanoparticles, as well this treatment showed that the greatest constant of degradation (<i>K</i> = 0.0628) and lowest half-life (t_1/2 = 11.3 days). In overall, the results showed that combined remediation strategies profoundly improve the bioremediation rate by indigenous microorganisms and further studies needs to evaluate different level of iron nanoparticles or even in combined with other remediation technologies. The results highlight the potential of combining biochar and iron nanoparticles for bioremediation, but the observed toxicity of nanoparticles at higher concentrations raises important questions. Further research should focus on understanding the underlying mechanisms of nanoparticle toxicity and their long-term effects on soil ecosystems.</p>