Wasilewski joined the Foxes in the summer of 2013 following a successful six-year spell with Anderlecht, where he lifted three Belgian league titles.
The powerful defender, whose new deal also includes the option of a one-year extension, has made 28 appearances in all competitions for the Foxes this season.
He played a vital role in his side’s surge to Barclays Premier League survival, helping them secure five clean sheets in their final seven fixtures.
Wasilewski made his Premier League debut against West Bromwich Albion in November, and netted his first goal in England’s top flight at Manchester United in January.