Victory over Longridge at Fox Lane saw them finish top of the table, 13 points clear of Garstang, who pushed them all the way.
The title-clinching win was a low-scoring affair with the bowlers very much having the better of it.
Asked to bat first, Leyland were 110-7 in 50 overs.
Karl Cross hit 27 at the top of the order, with their top scorer being Nathan McDonnell with an unbeaten knock of 33.
It was steady scoring from McDonnell who faced 89 balls and hit two fours.
McDonnell was then to take four wickets with the ball as Leyland tore through the Longridge batting.
The visitors were bowled out for 44 in 20.2 overs, with only two batsman making it into double figures.
McDonnell took 4-6 from 4.2 overs, Ross Bretherton taking 4-18.
Leyland had last won the title in 2016 and before that in 2013 and 2010.
Garstang beat St Annes to take the runners-up spot, that a fine achievement in just their second year at this level. They won by eight wickets, bowling out St Annes for 92 – Ian Walling took 5-35 and Travis Pieters 4-30.
Garstang chased down their target inside 27 overs, Michael Walling unbeaten on 36 and Punit Bisht 28 not out.
Last season’s champions Blackpool finished third after a final-day win over Fulwood and Broughton.
Runs were in short supply at Stanley Park, Blackpool all out for 93 after batting first with Jon Fenton taking 4-58.
But F&B were skittled out for 55 in reply, seven of the wickets were claimed by Matthew Grindley.
There was an eight-wicket win for Chorley against Fleetwood at Windsor Park.
They invited their visitors to bat first and bowled them out for 76 inside 31 overs. James Lee took 5-29 and Chamikara Edirisinghe 3-16.
In reply, Chorley were 77-2, Edwin Moulton seeing them home with an unbeaten 32.
Opener Stuart Naden had struck 30, the victory seeing Chorley finish seventh.
Kendal won their derby with Netherfield at Parkside Road, a third victory on the bounce seeing them avoid relegation.
In the battle of the bottom two, Barrow won their visit to Penrith by 54 runs but still finished marooned at the foot of the table.