On 18 January 2007, after struggling to establish himself in the first team at Watford, Spring rejoined Luton on a two-and-a-half-year contract for a transfer fee of £200,000 (rising to £300,000). His first game since returning to the club came on 30 January in the 1–0 away defeat to Coventry City. At the end of the season, Luton were relegated to League One after two seasons in the Championship, with Spring making 14 appearances, scoring one goal. During the 2007–08 season, Spring made 54 appearances, scoring 12 goals, as Luton were relegated again to League Two.