After returning from studies abroad, in Cologne and Rome, he was in 1513 elected vicar in Linköping. One year later he became Archbishop of Uppsala. In 1515 he got into an argument with the Swedish regent Sten Sture the Younger, who spread the rumour that he was allied with the King Christian II of Denmark. True or not, it resulted in Trolle being removed from his office and put under siege in the archbishops mansion Almarestäket at lake Mälaren. In the winter of 1517, Almarestäket was demolished by orders from the Swedish government. The Danish threat grew stronger, and Trolle was among those who spoke in favour of the Danish King. In 1520, Christian II of Denmark entered Sweden, and Trolle was rewarded by being reappointed Archbishop of Uppsala. He crowned Christian King of Sweden on November 4, 1520. This, and subsequent events, supports the notion of the two having made a deal previous to Christian's conquest of Sweden.
Gustav Trolle presented a list of antagonists who had caused him to suffer and who had ordered the demolition of Almarestäket. King Christian gathered several people (some sources say 100, other say 20), and had them executed at the so-called Bloodbath of Stockholm on November 10, 1520. The details and death toll are uncertain, for Christian himself wanted the public execution to have as strong effect as possible, and later, King Gustav I of Sweden is likely to have boosted the figures to support his Danish War.
Christian returned home a few months later and Trolle was one of those put in charge of the government. But he was unpopular, and in September the following year he was forced to leave Sweden, and move to Denmark where he lived for several years. In 1526 he then met with Christian in the Netherlands. Christian had been dethroned from Denmark, but was eager to get back in power. He renounced his Lutheran faith so that he could gain the support of the Catholic Church. He gathered an army and marched to conquer Norway in 1530.
He was described by Olaus Petri as a stiff and obstinate man. For a long time after his death, he was regarded as a traitor to the Swedish people. This was also the prevailing view among the Swedish 19th-century historians such as Anders Fryxell.
- (Swedish) Nordisk familjebok, in Swedish