The 30-year-old will be tied to the Portuguese club for the next 18 months, with an option to extend the deal for two more years, reports Xinhua news agency.
Sporting said the contract also includes a 60 million euro ($73.2 million) buyout clause.
"(We) wish Fredy Montero all best professionally and personally," Sporting said on their official website on Wednesday.
It will be Montero's second spell with the Lisbon outfit, whom he also represented for two and a half years before joining Tianjin Teda in early 2016.
He spent a year with the Chinese club before being loaned out to the Vancouver Whitecaps last year.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
