Bailey first struck after four minutes, thundering in a shot from outside the box and from a tight angle past keeper Oliver Baumann.
The 23-year-old winger then intercepted an inexplicable 30-metre back pass from Andrej Kramaric to beat the keeper again for his fourth goal of the campaign.
The Jamaican had also scored twice in their midweek 4-0 win over Slavia Prague in the Europa League. Leverkusen, who were missing half a dozen players to injury and COVID-19, were caught napping when Christoph Baumgartner was left unmarked to charge forward and curl in a shot to cut the deficit in the 50th.
Leverkusen’s 17-year-old Florian Wirtz, however, restored their two-goal lead five minutes later with a solo effort before Hoffenheim’s Florian Grillitsch was sent off with a second booking in the 65th.
A stoppage-time penalty from Lucas Alario sealed their seventh win in the last eight games.