Porto seal deal for Moutinho
Porto added that central defender Nuno Andre Coelho will move to Sporting as part of the agreement.
Moutinho attended Sporting's youth academy and made his debut for the senior side aged 19. He was made captain the following season, becoming the club's youngest skipper.
The 23 year-old was a consistent performer for the Lisbon club for several seasons and posted a club record of 100 consecutive appearances between 2006 and 2007.
Last season was, however, a turbulent one for Sporting with the side finishing fourth in the league after successive runner-up spots.
Moutinho's lacklustre performances during the season resulted in Portugal coach leaving the player, who has 25 caps, out of the squad for the World Cup finals in South Africa, even though he played a key role in the qualifiers.
According to local media, Moutinho fell out with Sporting's football director and former Portugal international Costinha last month, with the latter threatening to strip the midfielder of the captain's armband.