In 1593, he served envoy of Sigismund Báthory to Christoph Teuffenbach, Captain General of Kassa (today: Košice, Slovakia).
After 1598, he moved to the Partium where served as familiar of Judge royal Stephen Báthory de Ecsed.
Imreffy joined to Stephen Bocskay's War of Independence and became a member of the Royal Council.
He successfully crushed the rebellion of Serb militia in Lippa (today: Lipova, Romania).
After the betrayal of István Kendi, who tried to murder Prince Gabriel, Imreffy was appointed Chancellor of Transylvania.