Marjan Kandus took up basketball in high school and played originally with his hometown team of Branik. He soon joined AŠK Olympia, however, and with them won Yugoslavian national titles in 1957, 1959, 1961, and 1962. During that time, he also represented Yugoslavia abroad, winning the tournament at the Mediterranean Games in 1959. The following year he competed at the 1960 Rome Olympics, where his nation placed sixth overall. He then competed at the 1961 European Championships, where Yugoslavia took home silver behind the Soviet Union. By career, he graduated with a degree in economics and worked in that capacity with Ljubljana Bank.