Canaries boss Paul Lambert has raided his former club to land the 25-year-old left-back, who was the Us' player of the year last season.
Tierney has put pen to paper on a two-and-a-half year deal at Carrow Road and could make his debut against Cardiff on Saturday.
"He's a top lad. He was great for me at Colchester," said Lambert.
Source: PA
Source: PA