The 28-year-old has agreed to sign for the Hatters on a two-year deal and Harford hopes the winger can help Luton make a quick return to the Football League following his back-to-back promotions with Peterborough and Brentford.
Harford told the club's official website: "I think it's a coup for Luton Town Football Club to sign a player of Adam's ilk.
"He's athletic, experienced and the kind of player we've been looking to bring to this football club for a long time.
"He can get to the by-line and deliver crosses and will use the balance and width in the side.
"At 28 he's in his prime and he's got the experience of winning promotion the last two seasons and he's come here to do it again."