The France forward has backed his new team-mate to drive Arsene Wenger's side onto further success, but only after a period of adjustment
Alexis has made three pre-season appearances for the club since moving from Barcelona and looks set to challenge Giroud for a place in the starting XI.
And France international Giroud, who came off the bench to score in Arsenal's Community Shield triumph over Manchester City on Sunday, believes that though it may take some time to get used to English football, Alexis will take the Premier League by storm.
"I've played with him in training," Giroud told the club's official website. "We have a good understanding - like Mesut [Ozil] when he signed for Arsenal. It's always easy to play with these kind of players.
"I think he will maybe need some more games to adapt his game to the Premier League but that's normal and he's a fantastic player so I think he will [have] a great season.
"He has different qualities to me, Yaya Sanogo and Joel Campbell. He can bring his pace and his technique in the centre of the park and he's a great finisher.
"We have a good quality squad and now the quantity too, so that's why I think we will be stronger this year."
Despite ending their nine-year trophy drought by winning the FA Cup in May, the Gunners were criticised for the way they fell away in the 2013-14 title race and were well beaten by the division's top sides.
But Giroud believes the depth that Wenger has added to the squad over the summer with four new signings, including Alexis, will take the north Londoners right to the wire.
"Last year we did well until March. We had a bad run after but we really wanted to come back and be stronger than last year," he added.
"I think when our Germans join us, we will be stronger for sure and hopefully [we can compete] until May."