Katsoulis began his
club career with
AO Dramas. He then played with
PAOK from 1974 to 1988, having a leading role in the team. In 1984, he won the
Greek Cup with PAOK, while playing in one of the most historic Greek Cup finals against
Aris. In 1988, he moved to Aris, and with them he won two
Greek League championships (1989, 1990) and 2 more Greek Cups (1989, 1990). With Aris, he also played in two
EuroLeague Final Fours (
1989 Munich and
1990 Zaragoza). In 1990, he moved to
Iraklis, and in 1993, he moved to
Makedonikos. He finished his pro club career with a total of 5,356 points scored in the
top-tier level Greek League. ==National team career==