The Glasgow-based side officially announced the signing of the 26-year-old from Dutch side VVV-Venlo on a five-year deal on deadline day.
The Greece international has been in amazing goalscoring form, finishing as the highest scorer the Dutch Eredivisie last season with 26 goals.
Giakoumakis insists that when he came to know about the interest from Postecoglou it made him realise that he was making the right choice.
“I’m really delighted to commit my long-term future to Celtic and I can’t wait to get started with my new team-mates”, the striker told his club’s official site.
“Celtic is one of the world’s great football clubs with the best fans around.
“It is a club I have admired for so long and it will now be an honour to wear this famous jersey.
“To know that the Manager wanted me so much to join Celtic is really humbling and it makes me know I have made the right choice.”
Giakoumakis is excited about the challenges his new team will face, both in Scotland as well as in Europe, and hopes that he will be able to help the team as much as possible.
“We have some exciting challenges this season in Scotland and in Europe
“I will be doing all I can to help the team as much as possible and bring our supporters success.”
The prolific striker turned down approaches from Saudi Arabia and Turkey to make the move to Celtic.
