The 23-year-old midfielder has agreed a three-year contract and links up with his former manager Gary Locke at Rugby Park.
Robinson made over 100 appearences for Hearts since his debut seven years ago but was handed just two league starts last season by Robbie Neilson as the Edinburgh side ran away with the Championship title.
Scott told the club’s website: “I am delighted to join Kilmarnock and I am looking forward to working with the manager again. This is a new challenge for me and I am ready for it.”
Locke said: “I am over the moon to have signed Scott. He is a tenacious player, great on the ball and makes good runs from the midfield.”