In 1724, he had become student in Uppsala University, and was by 1734 appointed assistant professor of Greek and Roman literature, after having disputed in 1732 with the thesis De magnetismo morum naturali.

Troilius moved to Stockholm in 1740 as court chaplain, and the following year became the confessor of the Swedish Royal Family.

In 1751, he was unanimously elected new Bishop of Västerås following the death of Andreas Kallsenius.

In 1760, Troilius also was elected a member of the Royal Swedish Academy of Sciences.

His son Uno von Troil (1746–1803) also served as Archbishop of Uppsala.