Haddadi announced his retirement from the Iranian national team at the 2023 Fiba World Cup, shortly after Iran lost to Lebanon 73-81 in Jakarta in early September.
The 38-year-old player, who joined Sichuan in 2023, will continue his playing career with the Chinese club.
He finished his final FIBA Basketball World Cup with averages 10 points, 6.3 rebounds, 3.5 assists and 1.6 blocks per game - moving into the top-five for blocks in World Cup history with 31 rejections.
Haddadi was the first Iranian to play in the National Basketball Association (NBA) when he debuted with the Memphis Grizzlies in 2008.