Soot and carbon dioxide released from internal combustion engines became the key issues when using fossil fuels. The use of zero-carbon fuel, ammonia, with hydrocarbon fuels may play an important role in reducing the exhaust effect on the environment and mitigating the reliance on nonrenewable energy resources. However, ammonia reduces the flame speed of hydrocarbon fuels. A numerical approach was executed to study the ammonia impact on n-heptane, a diesel surrogate, flame. A kinetic mechanism was prepared by adding the sub-mechanism of ammonia, NO2 and NO3 emissions, and soot precursors to the n-heptane kinetic mechanism. The modified Arrhenius equation and soot surface reactions were used to study the soot formation with NOx emissions. The results showed that ammonia decreased the fractions of carbon-related species and raised the concentration of non-carbon-related species. Therefore, CO and CO2 emission species reduced, whereas the fraction of non-emission species, H2O, increased at the end of combustion. From 0% to 50% addition of NH3 in n-heptane fuel deteriorated about 36% soot and NO3 emissions with only a 17% reduction in the laminar burning velocity. When the ammonia contents increased from 50% to 90%, the reduction in exhaust gas emissions and the burning velocity were around 57% and 37%, respectively. It is concluded by the current study that the dilution of ammonia in n-heptane fuel should be equal to or less than 50% because a higher reduction in CO, CO2 and NOX emissions can be achieved with a small reduction in burning velocity.