The Sounders on Thursday announced the sale of Montero to Sporting CP, which exercised its option to buy the on-loan Colombian striker. Montero joined the Lisbon club in July, scoring 13 goals this season to lead the Portuguese top flight.
"Fredy has been and will always be a special member of our family," said Sounders general manager Adrian Hanauer in a news release. "Fredy had a wonderful career in Seattle and is continuing that success overseas. Hopefully his quality of play gives him an opportunity to be added to the Colombia World Cup roster. We wish him well with this next chapter of his career."
Montero, 26, hasn't played for the Sounders since the end of the 2012 campaign. Following four seasons with Seattle, during which he scored 47 league goals and earned three All-Star selections, Montero spent the 2013 season on loan with Colombian side Millonarios.