In 1944 Pareja was appointed as Ecuador's chargé d'affaires in Mexico. In 1945 he became a special representative for the United Nations Relief and Rehabilitation Administration (UNRRA) in Washington D.C.. He later served in Montevideo and Buenos Aires, coordinating for the governments of México, Central American nations, Argentina, Uruguay, and Paraguay.
Pareja's cycle of narrative fiction was marked by realism and a strong connection with the history of his country (El muelle [“The Pier”], 1933; Hombres sin tiempo [“Men Without Time”], 1941; Las tres ratas [The Three Rats], 1944). Having established a reputation as a writer both inside and outside of Ecuador, in 1944 he published an important biographical novel, The Barbaric Bonfire, about the actions and historical circumstances surrounding the life and death of General Eloy Alfaro.