After a first half that won't live long in the memory, Bailey stepped up three minutes into the second half, scoring with a fantastic strike into the top corner of the net.
After going in front it looked only a matter of time until they got the second goal and that proved right as Wendell doubled the scoring from the penalty spot.
There weren't any more goals in the game despite the hosts looking dangerous everytime they went forward but they will take the win as that means they now sit second in the table, while the visitors are now only four points off the relegation zone.
Defensive gameplan from the visitors saw the first half half go by without any goalmouth action
Both sides really struggled to get their football going in the first half as the visitors gameplan was to come to the BayArena and defend to try and come away with a point.
It meant that it was up to the hosts to try and breakdown the visitors and despite getting into great positions on a number of occasions the thing that was lacking was the final ball which saw the sides go in at the break goalless in a half that won't be remembered.
Bailey opened the scoring just after half-time with a superb strike
Whatever was said at half-time though by Leverkusen manager Heiko Herrlich worked almost instantly as the home side took the lead three minutes after the restart.
The goal came in spectacular fashion as Bailey received the ball along way out from goal before unleashing a fantastic stike with his left foot which flew into the top corner of the net leaving Robin Zentner with no chance in goal.
After taking the lead, the hosts really started to ramp up the pressure on their opponents and they went so close to doubling the score when Julian Brandt this time picked up the ball a long way out before unleashing a right footed shot which went just wide of the goal with Zenter struggling.
Wendell sealed all three points for the hosts from the penalty spot
The longer the game went on the harder it got for the Mainz players and that gave the home side space and they doubled the scoring from the penalty spot.
Wendell calmly slotted the ball into the back of the net from the spot after referee Frank Willenborg gave the spot kick after Giulio Donati was adjudged to have fouled Kevin Volland.
The hosts had further chances through Lucas Alario to score even more goals but it just wasn't the striker's day in front of goal but it didn't matter much as Leverkusen secured the three points which they were after, while the visitors know they must improve in the upcoming weeks or they will fall into the relegation zone.