The Heed fell to a narrow defeat at the 1st Cloud Arena in final game of pre-season.
Gateshead, who had tasted victory in each of their previous friendlies, took an early lead through Adam Campbell.
Robert Briggs got the equaliser midway through the second 45, before Sam Hodgson came off the bench to land the winner.
Opening the game on three minutes, Connor Tee floated in a cross for Alex Kempster, but the former Whitley Bay winger could only head into the hands of Jacob Chapman.
The Heed pressed the hosts and forced an error on 10 minutes, breaking the deadlock through Campbell.
After winning the ball high up the pitch, Cedwyn Scott squared to the former Darlington man to blast into the back of the net.
Greg Olley’s long-ranged effort flew over the target moments later, while Nathan Lowe saw a hopeful strike stopped by Chapman.
The thrilling start to the game continued and Graham Fenton’s side thought they equalised on 15 minutes, but Jon Shaw’s header was ruled out for offside.
Almost instantly, Shaw again came close from a corner, and Chapman could only parry to Dillon Morse.
The ex-Gateshead defender was denied magnificently from the head of Macaulay Langstaff on the line.
In end-to-end fashion, Olley played Langstaff to calmly poke past the ‘keeper, but the chance was kept out by Shaw mere inches from crossing the line.
On the half-hour, Olley skilled his way past Lowe before firing over from just inside the area.
Two minutes later, a dipping cross found an open Blair Adams, who volleyed over the bar for The Mariners.
Ntumba Massanka and Briggs had efforts blocked by The Heed backline on the brink of half-time, while the former couldn’t stretch out far enough to connect with a cross in the second period.
On the hour mark, Macauley Langstaff found a darting Scott, but Myles Boney got the better of the striker one-on-one.
Owen Bailey drilled a chance wide soon later, before South Shields pegged back level.
Lowe’s corner was powerfully nodded past Chapman by Briggs at the front post with 71 on the clock.
The Mariners’ next attack saw Darius Osei bolt down the wing before feeding Hodgson for an easy finish to take the lead.
Osei came close himself on two occasions in the following stages, but two strong saves from Chapman prevented the striker.
Hodgson nearly notched another late in the day as Kempster picked out the forward in space, but his shot from close-range soared over.
South Shields XI: Boney, Adams (Kempster, 77’), Trialist (Bodenham, 25’), Shaw (Morse 67’), Morse (Trialist, 45’), Hunter (Jenkins, 77’), Ross (Lowe, 67’), Lowe (Tee, 45’), Tee (Briggs, 25’), Kempster (Osei, 32’), Massanka (Hodgson, 67’)
Unused subs:: Steavens, Agnew, McGowan, Rossiter
Goals: Briggs (71’), Hodgson (74’)
Gateshead XI: Chapman, Trialist (Pani, 65’), Wombwell (Trialist, 75’), Storey, Tinkler (Bolton, 84’), Bailey, Greenfield, Olley Campbell (Trialist, 61’), Scott, Langstaff
Unused subs: Cameron
Goals: Campbell (10’)