The Pilgrims started brightly at Evesham United’s Jubilee Stadium but fell behind to Joe Parker’s 11th minute strike.
They fell further adrift when Joe Hanks converted a dubious penalty 12 minutes later and wrapped up all three points when Parker bagged his second nine minutes from time.
It was not a result which appeared to be on the cards when a United side showing five changes to their last outing made a blistering start.
Dominic Knowles converted Ben Middleton’s low cross in the second minute but was adjudged offside before Nicky Walker burst way from Vinny Harper to drag an effort across goal and wide three minutes later.
Harper’s subsequent clearance clattered into Knowles but rolled agonisingly wide for the Pilgrims.
The Tigers defied United’s early dominance to take the lead when Fabien Robert threaded the ball through for PARKER to beat Peter Crook with an angled finish.
Matters got even worse for the Pilgrims when Middleton and Walker tangled with Harper and referee Daniel Locker awarded a spot-kick, which was crashed home by HANKS.
Zach Jeacock in the Gloucester goal made a terrific save to keep out Knowles following a quick Platt free-kick, while Crook made a fine stop to tip Luke Russe’s long-range drive on to the post.
United threw three substitutes on at half-time and George Green’s free-kick delivery found Luke Shiels, who hooked an effort over the bar from close-range.
Andi Thanoj rattled the post from 20 yards and debutant Jordan Adebayo-Smith curled the rebound narrowly wide as United started to build a head of steam.
United’s hopes were well and truly extinguished when Josh Thomas motored from a Boston corner and PARKER blasted home City’s third.
There was still time for Simon Ainge to hit the post with a header from Walker’s corner, but the game was long since up for the Pilgrims.
Gloucester (4-4-2): Zach Jeacock; Josh Thomas, Spencer Hamilton, Sam Avery, Vinny Harper; Luke Russe, Chris Knowles (Kieran Smith 90), Joe Hanks, Fabien Robert (Alex Hainault 66); Joe Parker (James Spruce 82), Zack Kotwica. Subs (not used): Ioan Richards, Tom King (gk).
Boston (4-4-2): Peter Crook; Ben Middleton, Luke Shiels, Simon Ainge, Alex Whittle (George Green 46); Nicky Walker, Tom Platt (Brad Abbott 46), Andi Thanoj, Ashley Jackson; Tom Clare (Jordan Adebayo-Smith 46), Dominic Knowles. Subs (not used): Karl Byrne, George Willis (gk).
Referee: Daniel Locker.