The win maintained Bayern's 100 percent Bundesliga home record after 10 games at the Allianz Arena and kept them eight points ahead of Borussia Dortmund, who beat Ingolstadt 2-0 on Saturday.
The Bavarians have won 17, drawn one and lost once in 19 Bundesliga games, scored 50 goals and conceded only nine in an almost embarrassing dominance of the Bundesliga as they close in on a fourth successive title.
Hoffenheim, who have won only twice, stayed one place off the bottom with 14 points.
Last season's runners-up VfL Wolfsburg extended their winless run to six matches when they were held 1-1 at home by Cologne in Sunday's other game.
Bayern created plenty of early chances in driving rain and Lewandowski put them ahead in the 32nd minute from close range from a chance set up by Douglas Costa's trickery on the left.
Bayern occasionally looked vulnerable and Andrej Kramaric, on loan from English Premier League leaders Leicester City, wasted two precious chances to equalise.
The Croat shot weakly at Manuel Neuer just before halftime and missed an even better chance after the break when he broke clear on the right and slipped his marker, only to fire wide with only Neuer to beat.
Lewandowski made Hoffenheim pay in the 64th minute when he ran onto Philipp Lahm's defence-splitting pass and dinked the ball over Oliver Baumann for the Poland forward's 19th league goal of the season.
Seventh-placed Wolfsburg appeared set to win for the first time this year when Julian Draxler volleyed home from Vierinha's cross in the 67th minute.
However, Cologne replied eight minutes later when Anthony Modeste curled the ball in from 15 metres for his ninth goal of the season.
(Writing by Brian Homewood in Berne; editing by Justin Palmer)
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