Born in Kukush, then in the Ottoman Empire, in his youth he was inspired by the ideals of revolutionaries as Vasil Levski and Hristo Botev, who envisioned the creation of Bulgarian republic of ethnic and religious equality, as part of an imagined Balkan Federation. Delchev graduated secondary education in Thessaloniki's Bulgarian male high school and entered the military academy in Sofia, but he had been dismissed from there, because of his leftist political persuasions. Then he returned as Bulgarian teacher to Ottoman Macedonia, to became immediately an activist of the newly found revolutionary movement in 1894.
Although, considering himself to be an inheritor of the Bulgarian revolutionary traditions, as committed republican Delchev was disillusioned by the reality in the post-liberation Bulgarian monarchy. Also by him, as by many Macedonian Bulgarians, originating from an area with mixed population, the idea of being ‘Macedonian’ acquired the importance of a certain native loyalty, that constructed a specific spirit of local patriotism and multi-ethnic regionalism. He maintained the slogan promoted by William Gladstone, "Macedonia for the Macedonians", consisting from all different nationalities, inhabiting the area. In this way, his outlook included a wide range of such disparate ideas as Bulgarian patriotism, Macedonian regionalism, anti-nationalism and incipient socialism.