He was born in Veles (then known by the name Köprülü) in the Kosovo vilayet of the Ottoman Empire (present-day North Macedonia) where he graduated from Bulgarian Exarchate's school.

After Bulgaria lost the war, the Bulgarian occupation of Vardar Macedonia ended and Brashnarov remained in the new Kingdom of Yugoslavia.

In a report from 2 July 1929, the Vienna newspaper Arbeiter Zeitung stated that the 50-year-old Macedonian Bulgarian Panko Brashnarov, was imprisoned in Maribor.

[8] From the start of the new Yugoslavia, these authorities organized frequent purges and trials of Macedonian communists and non-party people were charged with autonomist deviation.

Many of the former left-wing IMRO government officials were purged from their positions, then isolated, arrested, imprisoned or executed on various (in many cases fabricated) charges including pro-Bulgarian leanings, demands for greater or complete independence of Yugoslav Macedonia, collaboration with the Cominform after the Tito-Stalin split in 1948, forming of conspirative political groups or organizations, demands for greater democracy and the like.

Initially, he cooperated with the new regime, but soon after had realized the defeats brought about by the Yugoslav Macedonism,[10] Brashnarov returned to the IMARO's ideas for Independent Macedonia.

[11] In 1948, being fully disappointed by the policy of the authorities, Brashnarov complained of it in letters to Joseph Stalin and to Georgi Dimitrov and asked for help, maintaining better relations with Bulgaria and the Soviet Union, and opposing the serbianization and Bulgarophobia spread amongst the Macedonian people.

As a result, he was arrested in 1950 as a Cominform agent under the accusation of "organizing an illegal group to support the Soviet Union in its conflict with Yugoslavia".