Ulster piled on the points during a Lions sin-binning before holding off a home fightback to win 39-37 in Johannesburg.
Dan McFarland’s side trailed 18-10 when Henco van Wyk was yellow-carded shortly before half-time, with Rob Baloucoune’s early try having been cancelled out by scores from Emmanuel Tshituka and Francke Horn.
However, Billy Burns, Rob Lyttle and Stuart McCloskey all went over in Van Wyk’s absence while Rob Herring added his own name to the scoresheet shortly after the centre’s return from the bin.
Tries from Andries Coetzee and Quan Horn plus a second for Francke Horn set up a tense finale but Ulster clung on to become the first northern hemisphere side to win in South Africa in the United Rugby Championship this season.
Baloucoune – back from Emerging Ireland duty for this fixture – scored the opening try inside two minutes.
Ulster won turnover ball just inside their own half and spread it wide to Baloucoune, who carved open the Lions with a step inside to sprint clear and touch down under the posts.
John Cooney added the extras before Gianni Lombard reduced the deficit with a long-range penalty.
Cooney’s first penalty went over off a post but the Lions were level when Ruan Dreyer’s superb offload sent Francke Horn charging over from halfway and Lombard converted.
Lombard gave the Lions the lead for the first time from the tee after 26 minutes and the home side looked to turn the screw as they repeatedly kicked penalties to the corner.
Their ambition paid off just after the half-hour mark when Tshituka crashed over from close range, although Lombard missed the conversion.
The Lions lost Van Wyk to the sin bin for a deliberate knock-on two minutes from half-time and Ulster took immediate advantage through Burns’ try. Cooney’s missed conversion meant Ulster trailed 18-15 at the break.
They were back in front less than two minutes into the second half when Lyttle had space on the left wing to dart over and Cooney rediscovered his range.
An unforced error from Marius Louw at a lineout opened the door for McCloskey to snatch the bonus-point try, with Cooney again on target to make it 29-18.
Herring then touched down from a driving maul, with Nathan Doak kicking his first conversion, before Coetzee brushed off Mike Lowry’s tackle to give the Lions hope.
Although the conversion was missed, Quan Horn added another score soon after and Jordan Hendrikse’s extras brought the Lions within six.
Doak split the posts with a penalty before Francke Horn’s second and another Hendrikse conversion made it a two-point game with two minutes to play but Ulster held on for their fourth win of the season.
