Henry Valois (1551–89) was elected king of the Polish–Lithuanian Commonwealth in 1573 and arrived in Poland in January 1574. After five months, Henry fled Poland–Lithuania upon inheriting the French throne from his brother, Charles IX. As Henry III of France, he was branded a violent tyrant, who allowed his mignons to run the kingdom and isolated himself from his subjects. Historians have done much to rehabilitate Henry's reputation, but his first experience of kingship in the Commonwealth has been neglected in these reassessments. This article uses the previously unstudied treasury accounts of Henry's Polish court to re-examine his experience of the Polish–Lithuanian elective, parliamentary monarchy as crucial to the development of his characteristic style of kingship and court. Some of these practices were a response to the challenges posed by the Polish political system to a newly elected king. This allows us to recover a lost political connection between Poland and France. Secondly, the article demonstrates Henry's active engagement in the Polish–Lithuanian politics, challenging the narrative that he was a passive king anticipating his return to Paris. Instead, Henry planned to cement his rule in Poland by mounting his own faction and pursuing a bold diplomatic agenda.