When the Spanish Civil War broke out, the Roosevelt Administration imposed a “moral” arms embargo against Spain. In January 1937, the embargo was legalized. This policy is usually explained by the strength of isolationism in national politics, by the influence of Catholic voters in the New Deal coalition and by the trend towards following the British lead among senior officials from the State Department. This work aims to analyze the Spanish policy of the Roosevelt Administration in relation to the Good Neighbor Policy in Latin America and the gradual abandonment of the policy of appeasement. The repeal of the embargo did not come until April 1939, when Washington recognized the new Franco regime, but the lessons learned in Spain proved decisive in the transformation of the American strategic thought of that era. Among other things, the fear of a repetition of the Spanish tragedy in Latin America, especially in Mexico, helped to prepare the country to get involved in World War II.