The 26-year-old had been offered a new deal at Partick Thistle but turned it down in favour of a move to Rugby Park.
Higginbotham has been playing in Scotland since he went on loan to Motherwell from Huddersfield Town in 2013.
After spending the last two seasons with Glasgow side Partick – scoring 10 goals in 74 appearances – he will now continue plying his trade in the SPFL Premiership in Ayrshire.
Higginbotham, who signed a two-year deal, is the third player to join Locke’s team this summer following former Hearts pair Scott Robinson and Jamie MacDonald.
He told Kilmarnock’s official website: “Gary has been relentless in his efforts to sign me and I have taken this as a huge compliment.”
Locke added: “I am over the moon to have secured Kallum as he was one of my main targets and we have chased him all summer.
“He is a creative front player – and a goal threat – and it’s great to secure him for the club.”