The 25-year-old France striker joined the Gunners from Montpellier this summer, as Arsène Wenger also swooped for Lukas Podolski and Santi Cazorla.
And Giroud’s France team-mate Koscielny, who also played alongside the forward at Tours, is convinced he will sparkle in his first season in north London and was thrilled to see him sign for the club.
“I am happy [he has joined the club] because he played very well at Montpellier,” Koscielny told Arsenal Player.
“I played with him at Tours and he was a great player then – now he is even more confident and scores a lot of goals. I know his qualities and he will give a lot for us.
“I know he has the physical quality to play in this league. For a striker it is [about] confidence and I am sure he is working hard to start well with Arsenal.
“He is tall, like Marouane Chamakh and is also good with his back to goal. I think if we play with technical guys he will be happy, and in the box he is a good finisher.”
Koscielny, who penned a new long-term deal with the Gunners this summer, believes he and Giroud have enjoyed similar careers to date and is expecting both to flourish under the guidance of Wenger.
“We have had the same career, and we had some difficulties when we were younger,” Koscielny continued. “Now it is better for us and we work a lot – we have found coaches who gave us confidence.
“I first met Olivier at Tours, where we played one year together. It was the first year for the club in the second division and we finished sixth – Olivier scored a lot of goals.
“After that I left for Lorient and he stayed one year, and he won the award for top scorer. After that he went to Montpellier and scored a lot of goals. He is a champion with Montpellier and I am very happy for him.”
MORE: Man United latest news
MORE: Arsenal latest news
MORE: Chelsea latest news
MORE: Liverpool latest news