Leicester City responded with a header from Japanese Shinji Okazaki to level things up before frontman Jamie Vardy put the Foxes infront with half an hour played.
Olivier Giroud came off the bench to head a late victor after Aaron Ramsey had brought Arsenal level at 3-3 following a Jamie Vardy double for the visitors.
Substitutes Aaron Ramsey and Olivier Giroud each scored in the final seven minutes to hand Arsenal a win over the 2016 champions.
"Lacazette is simple - in every game he's stronger since he joined us", said Wenger, who had seen his side lose at home in three of their previous four opening league fixtures. "Leicester had three shots on target and scored three goals, so that shows you how efficient they were".
If you have never seen a Premier League game and chose to start watching this season, take note that this isn't a normal situation.
Even if the thrilling attacks were aided by such fragile defending.
And the Arsenal legend is eager to see how the Nigeria worldwide can form a lethal combination with Jamie Vardy and keep Shinji Okazaki on his toes when the new campaign starts.
Arsenal wanted a penalty for handball against Wilfred Ndidi with referee Mike Dean unmoved, but the equaliser came on the stroke of half-time after Kolasinac squared to Welbeck with the goal gaping.
"I think we have all seen the amusing business of the transfer window and we never know what is round the corner".
Instead, Wenger avoided a third consecutive season-opening loss at the start of his new two-year contract.
Arsenals fans will be hoping this was a one off from Cech and that his fortunes, along with his performances, change for the better.
Meanwhile, Liverpool will play Watford at 11.30 tonight.
However, Arsenal's defense were still on their summer break.
The game seemed to be playing out to a rather tiresome finish with Arsenal not being able to create any chances and the Foxes happy to sit back on their lead.
In the 67th minute Giroud and Ramsey were brought on for Elneny and Holding, and those men would help turn the tide in Arsenal's favor.
Arsenal supporters and the on-looking injured Alexis Sanchez must have felt they'd seen it all before, as poor marking, positioning and organisation presented the visitors with three clear-cut chances they gladly seized.
And then minutes later, this.