Financial development market (FMD) may have positive or negative environmental consequences. This research investigated the effects of FMD and income on CO2 emissions in Gulf Cooperation Council (GCC) countries during 1980-2018. We found that income had positive effect but FMD had insignificant impact on emissions in GCC panel. Then, we tested these effects in the individual country time series and found that income had positive impact in Saudi Arabia, Kuwait and Oman and had insignificant effect in other GCC countries in long run. Effect of FMD was positive in Oman, was negative in UAE and was insignificant in rest of GCC countries. Effect of income was positive in Saudi Arabia and Kuwait and was insignificant for other countries in short run. The effect of FMD was positive in Kuwait and was negative in UAE. We recommend UAE to expand the financial market and suggest Oman and Kuwait to have a check on the financially supported pollution-oriented activities.