The 32-year-old, who most recently played for Cardiff City, joined the Foxes on a two-year deal. He started his career with Huddersfield Town, where he spent eight seasons, making over 200 appearances for the Terriers.
A switch to Queens Park Rangers followed in 2015, with Smithies spending three years at Loftus Road before moving to South Wales in 2018. While at Cardiff, the shot-stopper established himself as an important figure, playing a total of 100 times for the Bluebirds in all competitions.