According to Greek media, police have found 800,000 euros - equivalent to almost 8.9 million kronor - in cash at the home of one of the suspects.
In addition to basketball manager Vangelis Liolios, a former player, a referee adviser and three referees have been arrested. One of them currently referees in the EuroLeague, which brings together major clubs in Europe.
According to the Greek news agency ANA, around 50 matches in the Greek top league and lower leagues - including youth and school championships - dating back to 2016 are under investigation.
The major club Panathinaikos says in a statement that it is considering legal action over lost titles and that it is "playing in a rotten system."