Cole, who won 107 England caps, was a free agent after his recent departure from LA Galaxy, and Lampard is confident the 38-year-old will boost Derby’s promotion drive.
“I’m delighted that we’ve been able to secure Ashley’s services for the rest of the season,” said the Derby manager, whose side are currently in sixth place in the Championship, the final play-off spot.
“He’s a fantastic player, a quality left-back, and he also brings great experience to the dressing room.
“I know him very well from our time together at Chelsea, and with England, and I also know what he can bring to the group and the influence he will have.”
Cole, who won multiple trophies alongside Lampard at Chelsea including the Champions League, said he relished the challenge.
“For me it was a no-brainer to come here and get involved in this great environment and hopefully push for promotion,” he said.
“I’m coming out of my comfort zone,” he added. “I could have stayed in the MLS and relaxed but no, I wanted to come here and again fight for something, fight for a good cause and try to make promotion.”