The 38-year-old Cole, who seemed set to retire after being released by Major League Soccer's LA Galaxy in October, described the decision to play for Lampard as a 'no-brainer'.
Cole brings plenty of experience to the table, having won 107 caps for England and made 682 appearances for a host of clubs including Arsenal, Chelsea and Roma.
"I'm delighted that we've been able to secure Ashley's services for the rest of the season," Lampard told Derby's website. "He's a fantastic player, a quality left-back, and he also brings great experience to the dressing room.
"I've made my feelings known over the last couple of days just how highly I think of Ashley and I have no doubt whatsoever he will be a positive addition to our squad."
Derby are currently in the final play-off position of sixth in the second-tier after beating Reading at home last weekend.
