After being knocked down, Leicester got right back up with a second Vardy goal to take the 3-2 lead. After Aaron Ramsey leveled in the 83rd minute, Giroud sealed the three points with a header inside two minutes on an evening of thrilling attacks gifted by fragile defending.
Alexandre Lacazette's arrival has bumped Giroud even further down the Arsenal pecking order, but having given the 30-year-old the chance to leave, Wenger was thrilled he chose to stay.
"Obviously I knew that I was going to have a chance so we tried to push", Giroudsaid. "In the end he made a decision to stay and it was one of the great days of the recent weeks for me. I know how important he is not only as a player but also in the group".
Arsenal were twice behind against Craig Shakespeare's side.
"I love the man and the player".
"This has happened to us the last three seasons here".
England striker Jamie Vardy stunned the Emirates with a neatly taken finish after an error from Xhaka, but Danny Welbeck levelled for Arsenal just before the break.
The future of Alexis Sanchez is unclear but Wenger has suggested he is prepared to keep the striker for a season and then let him leave on a free if he will not sign a £300,000-a-week contract.
Okazaki, who headed home by the far post from a short corner, was pleased he scored on opening night but was not about to get carried away.
"If you were a manager, you're on the bench when you're 3-2 down with 20 minutes to go, and you win 4-3, you're more happy than concerned", Wenger said.
Giroud, 30, started just 11 Premier League matches last season and scored 12 goals.
"We were quite good a year ago on corners".
The Germany worldwide appeared to handle the ball during the build to Aaron Ramsey's late equaliser.
Cech initially tipped over Riyad Mahrez's shot but the latter turned provider from the resulting corner. "We see players like Hector Bellerin, Alex Iwobi coming through, Reiss Nelson and Joe Willock have had a fantastic pre-season".
Wenger 'relieved' Giroud has chose to stay
I keep the faith and I still believe I can have an important part to play this season in the club. In the end he chose to stay and it was one of the great days of the recent weeks for me.
Burney puts the sword to reigning EPL champions Chelsea
I have to try to adapt a new system and to anticipate this situation of playing with nine or 10 men in the next game. NAN also reports that Wayne Rooney scored the winning goal on his top-flight return to Everton after 13 years.
Wall Street lower on US-North Korea tensions
The data comes amid tepid inflation that has remained below the Federal Reserve's 2 percent target, despite low unemployment. The local currency closed at 1,143.50 won against the USA dollar, down 1.50 won from the previous session's close.