This paper employs panel smooth transition regression models to investigate the nonlinear effects of two monetary policy proxies (i.e., real exchange rate return and real interest rate differential) on the international reserves – macroeconomic variables nexus. The panel data set includes the fourteen G-20 countries during the period 1991-2012. Empirical results show that the marginal effects of the macroeconomic variables (savings, terms of trade, public debt, capital account liberalisation, economic growth, and trade openness) on international reserves are non-linear and vary with time, the proxies and countries, not linear and constant derived from traditional linear model. Currency devaluation policy (against the US dollar) can non-linearly enlarge the positive contribution of trade openness and public debt on international reserves, and non-linearly reduce the negative impact of terms of trade on international reserves, as the Marshall-Lerner condition holds. Expansionary monetary policy (through the decrease in domestic interest rates) can strengthen the positive effects of public debt, trade openness, and economic growth on international reserves. The precautionary and mercantilist views of reserves holdings are partially supported.