Karagounis arrives in the Netherlands from Atromitos in his homeland, having scored 12 goals in 96 appearances for the Greek Super League side.
He has also made three UEFA Europa League appearances, scoring in a qualifier against AZ in August.
PEC technical director Gerard Nijkamp believes that the player will be a valuable addition to Zwolle's squad, telling the club's official website: "We have (in) recent months thoroughly examined (Thanasis) and see in him a good reinforcement.
"PEC Zwolle is also very enthusiastic about his (arrival)."
The Dutch club also revealed that sides in the Bundesliga and the Championship in England had been interested in signing Karagounis, who has appeared for his country at both under-19 and under-21 level.
Ron Jans' side led the Eredivisie in September but have been in freefall ever since, winning just one of their last 14 league matches – form that has seen them drop to 11th.
