Officer John Franzen was driving south on Highway 680 near Walnut Creek, Calif., when he spotted the female dog on the concrete median in the middle of the road.
Franzen and his partner managed to coax the chihuahua to safety.
"This little dog needed some help off I-680 freeway today. We're glad he's safe," the Contra Costa California Highway Patrol tweeted Friday.
"We are keeping a close eye on her condition and will post another update when we know more. She may already have a home if her owner doesn't come for her!" the agency said in a Facebook post.
Officials don't know why the dog was running around on the highway, but animal services said that she would have been left there.
"It is possible she was found and dumped there," they said on Facebook.