In an uneventful first half, James Dobson saw a free kick from 30 yards turned away by goalkeeper Charlie Hurlock, whilst former Rebels striker Simon Martin headed over the bar for Hitchin.
Jake Somerville was alert to make a good block from Hitchin dangerman Matt Lench, and Dobson volleyed a good chance over late in the half, before Hitchin striker Nat Peacock missed a clear chance.
Slough started the second half brighter, and Johnnie Dyer headed over the bar before the Rebels took the lead on 50 minutes, Eddie Smith expertly heading Jake Parsons' cross past Hurlock. The Slough marksman picked up an award before kick-off to mark his 100th appearance for the club at Merthyr the previous Tuesday.
The score was harsh on Hitchin, who had the better of the overall play, but the visitors were only trailing for ten minutes. Following a well worked passage of play, Lench was on hand to fire past Somerville to level the scores. The goal owed a great deal to Martin, whose cushioned touch after a ball in from Dan Webb set him up.
Peacock came close to putting Hitchin in front on 67 minutes, with Somerville scurrying across his goal to push away the striker's header, and then soon after, Peacock looked to have been fouled by the last defender, but the referee chose to ignore Hitchin's claims for a free kick.
Slough tightened up the midfield as Hitchin continued to look the more likely, with the introduction of Adrian Sear and Luke Knight for wide men Dobson and Jake Parsons - and eight minutes from time, Jeffreys capitalised on hesitant Hitchin marking, with centre back Webb off the pitch receiving treatment, to head an inch-perfect free kick delivery from Knight past Hurlock.
The win lifts Slough up to eighth place in the league, with the Rebels having rode their luck to earn all three points.
Hitchin Town Line up
Charlie Hurlock, Harry O'Malley, Dave Corran, Alasan Ann (c), Dan Webb, Sam Barker, Dan Green (Michael Noone), Matt Lench, Simon Martin, Nat Peacock, Lewis Rolfe. Subs not used: Jack Waldren, Tinashe Chabata, Brett Donnelly, Tahj Bell.