This paper examines gender equality in environmental issues for achieving sustainable peace and security in Nigeria. The study adopts an ex-post facto research design. The findings confirm the age-long devastating effects of human exploitation of land and its resources. It discovers that enhanced peace and security (proxied by defense expenditure) leads to improved environment (reduced Co2 emissions) and that gender equality improves environment as a result of reduction in Co2 emissions due to gender mainstreaming on environmental management. Similarly, it also discovers that increase in the quality of governance which is control for corruption [CC]) will decrease Co2 emissions and indicates that good governance leads to reduced Co2 emissions and thus, better environment but on the... contrary, age index leads to an increase in Co2 emissions. Since the moderating effects of environmental impact assessment curtails Co2 emissions from high industrialization, environmental impact assessment should be mandatory for every firm that would be established. Also, government should increase defense budget, design new industrial policies, ensure gender mainstreaming, intensify anti-corruption fight and enact environmental sustainability laws to reduce Co2 emissions, and improve environment with the ultimate target of attaining peace and security in Nigeria.