15:00 09 Aug 2019
The North London club completed the signing of the Scotland international on Thursday.
Arsenal had two bids rejected by the Scottish Premiership club before finally getting their man on transfer deadline day.
Tierney has signed a five-year contract to keep him at the club until 2024.
Read more: Arsenal confirm Koscielny departure
“It’s a hard decision to leave a club that you love so much. People need to know that,” Tierney said on leaving Celtic.
Tierney scored eight goals and assisted a further 37 in 170 appearances for the club, playing an integral part in four league title wins, having come through the the Scottish champions youth academy.
The 22-year-old will not make his Arsenal debut this weekend after recently undergoing a double hernia operation, and is only expected to return at the start of October.