Scott Title claimed four wickets for the loss off 33 runs at Seas End Hall and the hosts were dismissed for 144.
Support came from Joe Peck, who took three wickets for the loss of 32 as Thomas Shorthouse added two wickets and Drew Harbron another.
Sleaford raced to a winning total of 145 without loss in the 27th over. Shaan Patel top scored with an unbeaten 83 while Aayush Patel added 59 to the tally.
In the South Lincs and Border League Premier, Sleaford Seconds secured a 44-run victory against visitors Freiston LL.
Tom Sanders' 68 not out was backed up by Sumnit Puri (37), Cameron hall (29) and Sam Burrows (19) as the hosts ended their 45 overs on 190 for 6.
Freiston were all out for 146, Hall taking four wickets and Burrows three.
Billingborough Firsts were beaten by six wickets as they hosted Woodhall Spa Seconds.
Newborough left Heckington with a 103-run success.
The hosts posted 234 for 5, but Heckington were dismissed for 131, Christopher Dobbie top scoring with 21.
In the SLBL Division One, Billingborough Seconds were beaten by eight wickets at Orton Park.
The hosts reached 67 for 2 after Billingborough were back in the pavilion for 66, Mark Pilgrim (19) top scoring.
Heckington Seconds won by three wickets at Spalding Seconds. Mitch Freeman's 102 helped the visitors to 226 for 7 after Spalding were dismissed for 225, Robbie Townsend taking three wickets.
Henry Cooper hit an unbeaten 124 and Ayush Patel scored 55 runs as Sleaford Sunday Firsts won by nine wickets at Woodhall Spa in the Lincoln and District League Premier Division.
The Spa men made 187 for 7 before the visitors responded with 190 for 1.
In Division One, Caythorpe beat visitors Billingborough by 42 runs. Joe Dickinson and Jack Butler (both 25) helped Caythorpe reach 105, the away side dismissed for 63.