The 27-year-old Real Madrid academy graduate will join Leicester City on a four-year deal, the Premier League champions have announced
The 27-year-old will officially move to the King Power Stadium on July 1 when his contract with the Liga club expires.
Hernandez is a product of the Real Madrid youth system and moved to Sporting in 2012.
He helped the club retain their top-flight status last season, making 36 starts including the full 90 minutes in the vital 2-0 final-day victory over Villarreal.
Hernandez is Leicester's second close-season signing after Germany international goalkeeper Ron-Robert Zieler as Claudio Ranieri seeks to add depth to his squad ahead of the forthcoming Champions League campaign.
The centre-back could face a tough task in dislodging captain Wes Morgan and Robert Huth from the Italian's first-choice XI after the duo starred at the heart of defence on the way to Premier League glory.
However, Huth will miss Leicester's opening trip to Hull City as he completes a three-match ban for violent conduct - a retrospective punishment relating to a clash with Marouane Fellaini during the 1-1 draw at Manchester United in May.