This paper estimates a new open economy macroeconomic model for South Korea to determine the output effect of currency devaluations. Three transmission mechanisms are considered: the expenditure-switching, the balance sheet, and a monetary channel associated to a nominal exchange rate target. Devaluations are defined as an increase in this target. This allows to isolate the effects of an explicit exogenous devaluationary policy shock. Ceteris paribus, a devaluation is found to be expansionary. Output contractions in South Korea should then be associated with a different shock such as an adverse shock on the international interest rate or on export demand.