Bartzokas' association with Olympiacos began in June 2012, marking the start of a highly successful period. In the 2012-13 season, he led the team to a EuroLeague championship, making history as the first Greek coach to win the title. He was named EuroLeague Coach of the Year in 2013 and also secured the FIBA Intercontinental Cup the same year.
In 2009, Bartzokas became the head coach of Maroussi and was named the Greek League Best Coach in 2010. He then took the helm at Panionios before joining Olympiacos in 2012. After his initial stint with Olympiacos, Bartzokas coached Lokomotiv Kuban, leading them to their first-ever EuroLeague Final Four appearance. He also had a brief tenure with FC Barcelona and a return to the VTB United League with Khimki.
Bartzokas' return to Olympiacos in January 2020 marked a new chapter. Despite the 2020-21 season being disrupted by the pandemic, he focused on rebuilding the team's roster. The following seasons saw Olympiacos achieve significant national and international success, including another Greek Cup victory in 2021 and a series of titles in 2022 and 2023.
Olympiacos' decision to extend Bartzokas' contract reflects their confidence in his ability to lead the team to further success. The club's management expressed their enthusiasm, highlighting his integral role in the team's achievements and his potential to steer them to new heights. As the longest-serving coach in Olympiacos' basketball history, Bartzokas continues to build on his legacy, aiming for even greater accomplishments in the upcoming seasons.