Foreign direct investment is important for financing, technology transfer, and reducing oil-dependent countries’ reliance on oil revenues. However, beyond economic factors, its attraction is influenced by institutional quality, the structure of economic power, and political and geopolitical uncertainties. Crony capitalism, by reducing competition and transparency and creating unequal access to economic opportunities, and geopolitical risk, by increasing uncertainty, can weaken foreign investment inflows. This study investigates the interactive effect of crony capitalism and geopolitical risk on foreign direct investment in nine selected OPEC countries over the period 2006–2024, using a quantile autoregressive distributed lag (QARDL) model. The long-run results indicate that crony capitalism has a negative effect on foreign direct investment across all quantiles, while geopolitical risk exerts a negative effect in the middle and upper quantiles. In the short run, the negative effects of both variables are observed in the lower quantile. The interaction between crony capitalism and geopolitical risk is positive in the long run. The marginal-effect analysis shows that, at the 0.50 and 0.75 quantiles, the negative effect of geopolitical risk persists up to crony-capitalism thresholds of 25.56 and 48.46, respectively; beyond these thresholds, the marginal effect of geopolitical risk may change sign. Accordingly, as geopolitical risk intensifies, productive and competitive investors tend to withdraw, whereas politically connected capital with preferential access to government contracts and oil rents is less sensitive to such risks. Therefore, the positive marginal effect at very high levels of crony capitalism reflects a distorted institutional structure and the dominance of rent-seeking investment, rather than an improvement in the investment environment. Reducing crony capitalism, improving institutional transparency, and managing geopolitical risks are thus essential for sustaining foreign direct investment inflows.