Recent studies indicate that Nigeria's CO2 budget was about 164 million tonnes (MTons) in 1990, of which the energy sector contributed close to 55%. It is expected that CO2 emissions emanating from the energy sector will increase from 90 MTons in 1990 to about 3 times this value in another 30 years, assuming a least-cost moderate development scenario. A number of viable CO2-mitigation options have already been identified in the energy sector, some of them the so-called 'win-win' options. As attractive as some of these options might appear, their implementation will depend on the removal of certain barriers. These barriers include a lack of legislative framework, a lack of awareness, a lack of access to appropriate technology, as well as inappropriate energy-pricing policies, among others. The paper presents an overview of Nigeria's energy-sector, the CO2 mitigation-options, the factors militating against implementation of the options, and some policy recommendations for removal of the barriers.