The main causes of the Spanish Civil War 1936—1939 lay in the domestic issues of the country. However, the involvement of certain leading European powers in the armed confrontation indicated that this war was far beyond the borders of the Iberian Peninsula, and it would be permissible to refer to it as an international armed conflict on the territory of Spain. The internationalization of the conflict was largely facilitated by Portugal, which from the first days of the rebellion (July 18, 1936) provided military, political, diplomatic, informational, trade and financial assistance to General Franco’s men. The common land border allowed the putchists to receive from the neighboring country all necessary military equipment, food, fuel as well as Portuguese infrastructure facilities, including airfields, sea and river ports, communication lines. The authoritarian regime of the Prime Minister A. Salazar provided such assistance bypassing international agreements of non-interference in Spanish affairs. The ideological proximity based on anti-communism, conservatism, nationalism and clericalism became the key factor to unite the regimes of Salazar and Franco in the struggle against the legitimate democratic government of the Spanish Republic. Based on the available factual material an attempt to reveal the importance and, in some cases, the decisive role of Portugal in the victory of “general-putchists” in the fratricidal war has been made in this article.