England lock Maro Itoje's return to action ended in defeat as champions Saracens suffered only a second loss of the league campaign.
Three Tom Homer penalties and a Max Clark try lifted Bath into second place as they edged out Saracens 14-11 at the Recreation Ground.
Wing Sean Maitland touched down for the Aviva Premiership leaders, while fly-half Alex Lozowski - he was also yellow-carded - kicked a penalty and drop-goal, before sending a 52-metre chance wide with the game's final kick.
European player of the year Itoje missed England's four-Test autumn series after breaking his right hand during Saracens' European Champions Cup clash against the Scarlets in late October.
A six week lay-off ensued, but he reappeared as Saracens looked to maintain their place at the Premiership summit, with his comeback arriving a week before they resume their European campaign through back-to-back games against Sale Sharks.
Itoje's selection was the headline team news, but Bath were also bolstered by wing Semesa Rokodoguni and lock Dave Attwood being released from England duty, while Wales internationals Luke Charteris and Taulupe Falteau also featured.
Homer kicked Bath into a sixth-minute lead as the home side dominated early territory and possession, only for Lozowski to tie things up midway through the first-half, before a second Homer strike - his 10th successful kick from the last 10 attempts - edged the home side back in front.
Bath's control had to tell in terms of a try, and they finally breached Saracens'defence when centre Ben Tapuai ran strongly before delivering a superb pass to his midfield partner Clark, who touched down.
Homer drifted the conversion wide, but Bath were good value for an 11-3 lead as Saracens, at times, struggled to repel their attacking fluency.
The visitors, from their most threatening spell of the first-half, went close to a try after pummelling Bath's forwards, but they could find no way through as Bath held out despite Faletau going off after he appeared to take an accidental finger in the eye.
Saracens, though, kept plugging away, and they reaped a reward just two minutes before the break when patient attacking play ended with Scotland international Maitland crossing wide out as Bath's lead was trimmed to three points.
And Saracens dominated the opening flurries of the second period, launching several attacks before they settled for a Lozowski drop-goal that levelled the score.
But Lozowski then blotted his copybook when he was sin-binned by referee Greg Garner for a high tackle on his opposite number Dan Bowden, and Homer kicked the resulting penalty for a 14-11 advantage.
Full-back Alex Goode, handed the kicking duties while Lozowski was off, missed a long-range chance to haul Saracens level, although it was the cue for a sustained spell of pressure.
Bath's poor kicking out of hand invited Saracens - led by Goode - to attack them - and it seemed only a matter of time before such territorial control would result in a try.
But no matter how much they huffed and puffed, Saracens could not find a way through and Bath held on for what could prove to be a significant victory in their quest for a title play-off spot.