This study investigates the effects of geopolitical risks (LJRI), the global uncertainty index (LDBI), and economic growth (GDP) on military expenditures in Turkey using the ARDL bounds testing approach and Toda–Yamamoto causality analysis. The results indicate a long-run cointegration relationship among the variables. Long-run coefficient estimates reveal that geopolitical risks and economic growth do not have a significant impact on military expenditures, while the global uncertainty index exhibits a significant negative effect, suggesting that increases in global uncertainty reduce Turkey’s military spending over the long term. In the short run, however, rising uncertainty is found to increase military expenditures, implying that although uncertainty initially imposes budgetary constraints, security concerns dominate in subsequent periods and lead to higher defense spending. Economic growth has a negative short-term effect, indicating that during periods of economic expansion, military spending can be relatively restrained, whereas during downturns, defense expenditures become more prioritized. The negative and significant error correction term confirms that short-term deviations from equilibrium are corrected over time. Toda–Yamamoto causality tests reveal no significant causality from geopolitical risks to military expenditures, but unidirectional causality exists from the global uncertainty index and economic growth to military expenditures. These findings suggest that Turkey’s defense budget is influenced more by global economic uncertainty and domestic economic capacity than by regional geopolitical risks. For policymakers, the results highlight the importance of adopting a flexible defense budget strategy that considers both security needs and macroeconomic stability, balancing short-term pressures with long-term fiscal sustainability.