Kosara Bokšan was born in Berlin in 1925. Three years later, the family moved to Belgrade.

She took art classes at Mladen Josić's school at the Kolarac People's University, then in Zora Petrović's studio in 1944. She entered the Academy of Fine Arts in Belgrade in 1945, in Ivan Tabaković's class. She was a member of the Zadar group (1947) consisting of seven students from the Academy of Fine Arts, including her future husband, Petar Omčikus.