A converted try to Blayke Brailey and 58th minute penalty goal to Nicho Hynes in the second half ensured the Sharks secured their ninth win of the season after both sides were locked at 10-10 after 40 minutes.
Cronulla were anything but convincing in the victory with a total of 16 errors but Hynes and halves partner Matt Moylan, who scored a try and had a hand in one, did enough to guide the side around the park.
The victory moves the Sharks in front of the Broncos in fourth spot on the Telstra Premiership ladder ahead of the representative round next week.