Second-tier runners-up last term, Scott Copley’s men followed up their opening-day success over Goldsborough with a convincing victory on home soil.
Andy Thompson (3-18) and Hamish McIntyre (3-31) were in fine form with the ball, helping get rid of Tanfield for 115 as Jake Stubbs hit a defiant 49.
An unbeaten half-century from Joe Horne (58 not out) then led Killinghall to 117/3 in 25.1 overs, Sam Halliday (35) also chipping in.
Arthington, last season’s Division Two winners, were unable to follow suit, losing out to Darley as the reigning champions got their own campaign up and running.
Beaten by Birstwith last weekend, the Crayke Lane outfit posted 247/5 from their 45 overs thanks largely to a knock of 84 from Jim Grange which included 10 fours and five sixes.
Adam Copeland (43) and Larry Audain (38 not out) also contributed, while Naveed Piran claimed four wickets.
Nathan Smith struck a fine 79 when Arthington took their turn at the crease, but he was the only visiting batsman to really get going as Joe Furniss (4-60) and Rob Nelson (3-5) combined to halt their response on 168.
Birstwith remain top of the pile after they recorded the most comprehensive of victories over Kirk Deighton.
Opening pair Sam Ryan (93) and Craig Robinson (90) were in imperious form as they shared an unbroken stand of 192 to guide the hosts to a 10-wicket triumph.
Earlier, Will Powell (37) and Thomas Conboy (32) had looked in decent touch for Deighton, helping their side to 188 all out.
James Johnston was the pick of the Birstwith attack, bagging 3-41.
Harrogate 3rds bounced back from their mauling by West Tanfield last time out, getting the better of Pateley Bridge in what was a close contest.
Tom Hardcastle’s 36 was the top score in the Badgers’ 173/8, spinner Dominic Bradburne knocking over three batsmen for Gate.
Bradburne (34) and Roosters captain Rob Stanwoth (32) kept the home side in the game before Matt Ingham (52) got them over the line in the final over of the match with two wickets in hand.
Tom Fryer performed superbly with ball in hand for Bridge, finishing up with a five-wicket haul.
An unplayable spell of bowling by Tom Wade paved the way for Helperby’s 10-wicket rout of Blubberhouses.
He helped himself to 5-12 alongside Simon Taylor (3-27) as the visitors were skittled with the meagre total of 60 on the board.
A rapid knock of 47 from 29 balls from Daniel Spink then saw Helperby wrap things up in 8.2 overs.
Goldsborough cruised to a routine seven-wicket win at Masham.
Having bowled their hosts out for just 116, men needed only 20 overs to knock off the required runs .