Guo Guangchang, dubbed "China's Warren Buffett", attended Fosun Group's annual meeting Monday morning, pictures posted by business magazine Caijing showed.
The publication quoted Guo as saying "there will be a better Fosun next year" during a speech at the event, without mentioning anything about the investigation.
Guo had been out of contact since Thursday and two of the group's listed arms in Shanghai said in statements last week the 48-year-old was "assisting in certain investigations" conducted by mainland authorities.
The statements stressed the probes had no "material adverse impact" on the finances or operations of the parent company and that Guo was able to take part in its decision making.
Caijing said Monday that Guo has "finalised" assisting in the inquiries and "returned home safely".
It was not immediately clear what the investigation was in relation to, but it comes as China targets the financial sector as part of a sweeping anti-graft campaign following a stock market rout that rocked global markets over the summer.
Fosun spokeswoman Valentina Wu declined to comment when contacted by AFP Monday.
Fosun Group is one of China's biggest private companies, and has interests in property, finance, pharmaceuticals, steel and entertainment, and has been aggressively buying assets in Europe and North America, including Club Med.
Police took Guo away at a Shanghai airport last week, according to Chinese media citing social media postings.
Other reports said he was being questioned in connection with a probe into former Shanghai vice mayor and director of the Shanghai Free Trade Zone Ai Baojun, who was placed under investigation last month by the Communist Party's internal anti-graft body for "severe disciplinary violations", a euphemism for corruption.
Ai's wife was allegedly investigated on suspicion of manipulating the stock market. She died of kidney failure a week before Ai fell.
Since coming to power Chinese President Xi Jinping has waged a much-publicised anti-corruption campaign that has ensnared a long list of officials, including the country's former security chief Zhou Yongkang.
Fosun Group is one of China's biggest private companies that has interests in property, finance, pharmaceuticals, steel and entertainment.
Guo is China's 17th richest person with a net worth of $5.6 billion, according to Bloomberg News. Fosun Group's flagship subsidiary, Fosun International, has net assets of 50 billion yuan ($7.8 billion).
Guo is a member of the Chinese People's Political Consultative Conference, a debating chamber that is part of the Communist Party-controlled governmental structure.
Shares in Fosun's listed subsidiaries in Hong Kong and Shanghai resumed trading Monday after being suspended on Friday.
By Monday closing, Fosun International plunged 9.45 percent in Hong Kong, while Fosun Pharmaceutical dropped 3.77 percent in Shanghai and dived 12.05 percent in the former British colony.
Fosun International bought renowned French holiday company Club Med earlier this year and in April was part of a consortium that acquired Canadian entertainment juggernaut Cirque du Soleil. It also has a stake in British-based tour operator Thomas Cook.