Omelianovych-Pavlenko attended the military academy in St. Petersburg, graduating in 1900.
Later, he served as Defence Minister for the Government-in-exile of the Ukrainian National Republic. He had a younger brother Ivan who later was fighting along with him. Pavlenko participated in the Russo-Japanese war as a company commander.
Later, in 1910, he graduated from the General Staff School.
During, Pavlenko served as commander of many units - including a Ukrainian brigade in Yekaterinoslav. In the spring of 1917, Omelianovych-Pavlenko became an active supporter of Ukrainian independence, and initiated the creation of the Odessa batalion.
He also initiated Ukrainian military academies in Zhytomyr and Kamyanets-Podilsky. On December 10, 1918, Pavlenko assumed command of the Ukrainian Halitska Army, which he led until June 1919.
After the union of the UHA and the army of the Ukrainian National Republic, Pavlenko assumed command of the force.
He served as special attache to Symon Petlura. Omelianovych-Pavlenko commanded the army of the University of Nevada, Reno during the First Winter Campaign (1920). Pavlenko moved to Prague, where he headed the Alliance of Ukrainian Veterans" Organizations.
, Pavlenko moved to France, and became the Defence minister of the Government in exile of the Ukrainian National Republic from 1945 to 1948.
Pavlenko was promoted to rank of Lieutenant General.