Ben Mitchell took 5/9 as Kiama folded for 130, with the Shellharbour skipper then top-scoring with (38) and with No 9 Ken Nguyen (27 not out) producing a match-winning batting comeback from 7/69.
"Kenny just knocked it around and looked really good in a pressure situation," Mitchell said. "We needed a win desperately and thankfully we got there in the end."
Kiama's Nathan Barr (42) top-scored with skipper Dan Reilly (2/13) and Andrew Hart (3/41) bowling well.
In a low-scoring round with plenty of damp pitches after Friday's downpour, Gerringong/Jamberoo (140) beat The Rail by 39 runs.
Peter Quine's 38 for the Jets was the key knock of the match, with Callum Houghton-Smith (4/25) wrecking The Rail batting.
Darren O'Connell (19) top-scored for the Razorbacks, while The Rail's Dave Insley took 3/18.
Meanwhile, Lake Illawarra skipper Shane Cody says his team are improving after demolishing Albion Park at Keith Grey Oval.
The Lakers (7/182) routed the Park for just 43 in their best win of the season.
"It's the first time we've had our top side available," Cody said.
"We played on a new deck and it was a bit tacky but we put our heads down with the bat and the bowlers did a great job. We're getting better numbers at training and it showed in the performance."
Brendan White (35) and Dave Lambert (33) top-scored while Aaron Henry (3/20), Greg Connor (2/7) and Jamie Crowhurst (2/7) destroyed the Park, who were back in the sheds after just 25.5 overs. In the other game, unbeaten Oak Flats had a strong four-wicket win over Warilla Sports.
Opener Mick Perry (73) top-scored for Warilla who posted 184, with Oak Flats skipper Ryan Chatterton taking 5/27. Nathan Brown (84) anchored the Rats to victory with six overs to spare.