The 23-year-old leaves Kenilworth Road after three seasons at the club, having joined the Hatters from Bedford Town in August 2010.
Walker made 36 appearances for the Town since making his debut in a 3-0 win over AFC Wimbledon in September 2010 but had enjoyed loan spells at Eastbourne, Cambridge, Southport and Braintree.
In total the forward netted five times in Luton colours, with four of those coming last season.
Everyone at Luton Town would like to wish Dan all the very best in his future career.