[5][6] In 1988 Olympiacos Women's Water Polo Team was founded and Katsoulis became the first ever head coach of the department.
[7][8] He remained head coach until 1993[5] and under his guidance, Olympiacos women's team became one of the top powers in the Greek League.
[5][7][9] In 2000 Katsoulis was appointed head coach of ANO Glyfada Women's Team and led the club to two Greek Championships (2000–01, 2001–02), the silver medal in the 2000–01 LEN Champions Cup (losing to Orizzonte Catania in the final) and the bronze medal in the 2001–02 LEN Champions Cup.
[7][10] In 2002 he was appointed head coach of NC Vouliagmeni Women's Team and led them to the 2002–03 LEN Trophy triumph, which was the first ever European title for the club.
[12][13][14] In 2016-17, he returned in Olympiakos assisting Haris Pavlides, reaching the Final of the Champions Cup in Kirishi, Russia, and winning the Championship in the Greek A1 women's League.