The opening goal came with just two minutes to go after Nacho Monreal crossed to Bacary Sagna, whose header was saved by David Marshall. Bendtner, however, was the quickest to react and prodded the ball home from point-blank range in the scruffiest of fashions.
With Cardiff's defense and hearts broken, Walcott then put the game to bed in injury time when he latched onto Jack Wilshers's sublime through ball to loft the ball over the advancing Marshall.
The Emirates Stadium, quite understandably, erupted with joy, elation and massive relief.
The win returns Arsenal to the top of the Premier League after Manchester City had won the early kickoff against Swansea.
Cardiff were excellent at the back with Steven Caulker and Kim Bo-Kyung putting in outstanding defensive performances. They frustrated Arsenal, who really looked like they had no answer to the questions they were posing.
The first half was best described as dire. Neither side were up to much in an attacking sense. Arsenal did not have a single shot on target and Cardiff managed just one. Walcott was the Gunners' most progressive player and tried to get behind the Bluebirds' deep defense, but Caulker and Co. were far too disciplined and never allowed the winger, or any other Arsenal player for that matter, any space.
Arsene Wenger would have given his team a rollicking at halftime, especially as Manchester City had returned to the top of the Premier League having beaten Cardiff's Welsh neighbors Swansea City.
However, the game started off at the same pedestrian pace and it really looked like injuries and fatigue were taking their toll on both teams.
The game turned in the 63rd minute when Bendtner was introduced for the ineffective Lukas Podolski. From there the Gunners pegged Cardiff's determined defense back and eked out the kind of chances that had been denied them during the previous hour.
It was not until Arsenal started going more direct that they broke down Cardiff's defensive barriers. Even then, Per Mertesacker and Jack Wilshere were denied by the post.
The Bendtner substitution proved masterful as Arsenal recorded a more-than-valuable victory.
Unfortunately for the giant Dane, he seemed to twist his ankle during his goal celebration and never returned to the field of play after receiving attention.
Read on as Bleacher Report offers six things we learned from Arsenal vs. Cardiff City...