Both sides scored four tries, but the 14 points off Jantjies’ boot trumped the nine contributed by the Cheetahs’ Joe Pietersen.
The Cheetahs went into the half-time break 10-7 up having shrugged off a nervous start to put the Lions under pressure by retaining possession with excellent phase play.
It seemed the Lions were in the mood to run rampant, but they failed to put the finishing touches to some good build-up work, and gradually the Cheetahs gained parity.
Having been disrupted by injury, the Cheetahs lacked coordination early on, but once they started to get their hands on the ball they recycled it confidently and struck back with a gem of a try.
It started with the Cheetahs’ taking the ball through 23 phases before Lions flanker Jaco Kriel won a crucial turnover on his own line.
Typically, the Lions decided to attack from deep, as Faf de Klerk tapped the ball to himself and launched an attack that swept 70m upfield.
Jantjies broke clean through, but when he was unable to link up with Warren Whiteley the ball popped loose and Pietersen snatched it up to send the attacking flow back the other way, offloading to Cornal Hendricks to run in the try.
Shortly before the break, Pietersen stood back to drop a goal – claiming the lead for the Cheetahs.
The Lions hadn’t expected to be trailing and coach Johan Ackermann must have read the riot act during the break – to good effect too, because within eight minutes of the second stanza the home side were 24-10 up.
Lionel Mapoe made a superb backflip after committing two tacklers to put Ruan Combrinck away for a long sprint to the line and, just two minutes later, it was Mapoe himself who did the honours with a long sprint to the line.
Jantjies added the conversions and a penalty and, from looking quite rattled, the Lions were suddenly 14 points up and in sight of their bonus point try.
But the Cheetahs were determined to show there was another cat in the fight.
The Lions became victims of their own confidence when they elected not to kick an easy penalty in the 55th minute to build on their lead, and in a flash found themselves back to level pegging.
The Cheetahs had hit back with tries by Francois Venter and Johann Sadie, and with Pietersen kicking both conversions, it was 24-all with 18 minutes left to play.
But the Cheetahs didn’t learn from the mistake made by the Lions and, when they also failed in an attempt to set up a try from a line-out try, the Lions broke back.
Jantjies gave restored their lead with a penalty before De Klerk scored a suberb try under the crossbar to finish off a strong run by Combrinck.
But the wild fluctuations continued and the Lions’ fans were still celebrating their team’s bonus point 10-point lead when the Cheetahs struck back with a try by Carel Greeff to make it 34-29.
. Other round 11 results: Waratahs 18-16 Rebels; Crusaders 29-15 Blues; Brumbies 31-18 Highlanders; Chiefs 35-27 Force.
. Round 12 fixtures: Highlanders vs Sharks; Brumbies vs Waratahs; Blues vs Western Force; Hurricanes vs Crusaders; Rebels vs Chiefs; Cheetahs vs Stormers; Bulls vs Lions.