The unbeaten competition leaders resisted a spirited second-half fightback from the Waratahs to consign Daryl Gibson's men to a fourth loss from six outings in 2017.
The Waratahs once again paid the price for a sloppy defensive display, missing a staggering 24 tackles in the first half alone and leaking two soft tries from lineout losses at Allianz Stadium.
Languishing in third-last spot on the ladder, things do not get any easier for the Waratahs, who travel to Wellington next to take on the defending champion Hurricanes on Friday night.
