During recent decades, the wasp spider, Argiope bruennichi (Scopoli, 1772), has expanded relatively quickly towards north Europe. As a consequence of its spreading, it is newly exposed to various factors of selection. We studied the impact of egg sac parasitoids on the mortality of A. bruennichi in three regions differing in climate conditions and time of settling by this spider. Parasitism of wasp spider egg sacs was relatively low (0–3.9%) and no significant differences between studied regions were found. One primary parasitoid, Tromatobia ornata, was reared; in approximately 60% of these parasitized cocoons, the entire content of the egg sac was destroyed.