Saint Mardarije was born Ivan Uskokovic in Podgoritsa, Montenegro, in 1889.  In 1907, he embraced monasticism at the Studenitsa Monastery and then relocated to Russia to study at the Saint Petersburg Theological Academy.  After graduation, he was ordained by the Russian Orthodox Church and sent as a missionary to America.  In 1919, he was one of five Serbian Orthodox priests who participated in the Second All-American Sobor, held in Cleveland, OH in February 1919, at which time it was recommended that the Serbian Church in Belgrade advance him to the episcopacy to organize a Serbian Orthodox Diocese in America.  Unfortunately, at this most chaotic time in the history of the Russian Orthodox Church, it was impossible to secure the written blessing of Patriarch [now Saint] Tikhon of Moscow.  Later in 1919, Archimandrite Mardarije returned to Belgrade, where he was assigned as head of the Rakovitsa Monastery and principal of its monastic school.  Subsequently, Bishop [now Saint] Nikolai [Velimirovic] of Ohrid was sent by Patriarch Dimitriye to administer the fledgling diocese.  Having likewise returned to America, Archimandrite Mardarije served as Saint Nikolai’s Deputy for two years, and continued to administer the diocese after the latter’s return to Belgrade.

On April 26, 1926, Archimandrite Mardarije was consecrated to the episcopacy in Belgrade.  Prior to his episcopal consecration, he had carried out most of the actual work of organizing the Serbian diocese.  He also served as parish priest in Chicago and purchased with his personal funds the land for Saint Sava Monastery in suburban Libertyville.

From the moment of his return to America, Bishop Mardarije undertook a wide range of ministries.  He did not spare himself, nor did he fear work, although he knew that he was gravely ill with an advancing case of tuberculosis.  In 1927, he convened the first National Church Assembly of the Serbian Orthodox American-Canadian Diocese to address a variety of organizational issues.  At a clergy conference held in Youngstown, OH in 1931, he renewed his appeal for all to work for the unity and good of the diocese.  His kindness, patience and reluctance to use punitive measures resulted in a great measure of unity within the diocese by the time of his repose on December 12, 1935 at the age of 46 years.  He was interred at Libertyville’s Saint Sava Monastery.