Gulf Cooperation Council (GCC) countries are highly dependent on hydrocarbons, which puts them at great risk to maintain stability in the long run. GCC countries need private investment to reduce their reliance on state and diversify their economies apart from hydrocarbon. The role of private investment is crucial to economic stability and development. Literature suggests that outward foreign direct investment (OFDI) can play a vital role in promoting private investment. Therefore, using feasible generalized least squares (FGLS) and panel corrected standard error (PCSE) techniques, we checked the impact of the GCC countries OFDI on private investment and found that OFDI significantly complement private investment in the GCC countries. The complementary impact of OFDI on private investment in the GCC countries can be used as a tool to promote private investment, diversify their economies and hedge against the pitfalls of addiction to the hydrocarbon.