A deal for Muscat to take over at his former Scottish club Rangers fell through last month, with the Australian coach keen to see out his season in China.
That determination paid off with another trophy for Muscat and assistants Ross Aloisi and Vincenzo Ierardo on Saturday.
Muscat's charges were two points clear of rivals Shanghai Shenhua ahead of the final round of games but claimed a 1-0 win over Dalian Zhixing, courtesy of Gabrielzinho's fourth-minute goal, to seal the title.
The 52-year-old last season became the first Australian head coach to win titles in Australia, Japan and China, and has now added another trophy to a resume that is already attracting plenty of interest.
Muscat, 52, was unsuccessfully sounded out for the Socceroos head coach role before Tony Popovic was ultimately appointed.
The Melburnian was on the verge of joining Rangers before that deal fell apart and appears certain to attract fresh interest in Europe and the UK after yet another title.
After finishing his playing days at Melbourne Victory, the hard-nosed defender started his coaching career as Ange Postecoglou's assistant at the same club.
Muscat grabbed the reins after Postecoglou took the Socceroos job and carved out a coaching legacy at Victory, winning two A-League grand finals, a premiership and an FFA Cup before quitting in May 2019.
After a short, ill-fated stint at Belgian club Sint-Truiden in 2020, Muscat was appointed manager of Marinos in July 2021, replacing now-Tottenham boss Postecoglou.
Muscat finished second in his first year at the helm, then won the league in 2022, before departing for China.
He will now turn his focus solely to reviving Shanghai's ailing Asian Champions League Elite campaign, which continues with Tuesday's game against FC Seoul.
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