After a goalless opening hour, Josh Donaldson broke the deadlock shortly after his introduction from the bench following the Magpies substitute's stretching finish from Jay Turner-Cooke's inviting free-kick before Nathan Tshikuna's thunderous volley levelled the Group C clash in the closing stages.
United's youngsters, though, gained an additional point after prevailing via penalties, with Ben Parkinson, Turner-Cooke, Donaldson, Johnny Emerson, Charlie McArthur and Leo Shahar all successful from 12 yards before Kai Williams' spot-kick struck the underside of the crossbar.
Diarmuid O'Carroll made four changes from the side which claimed a 3-1 away win against Leeds United in Friday's Premier League 2 clash as Australia international Garang Kuol, Travis Hernes, Shahar and Anthony Munda were all handed starts against the National League outfit.
Aiming to build on a 2-1 comeback victory away at FC Halifax Town last month, McArthur went close to netting his second goal in as many matches at under-21 level.
The Scotland under-19 international, who joined the Magpies from hometown club Kilmarnock in the summer of 2022, latched onto Leo Shahar's teasing free-kick inside the box but the unmarked centre-back fired his volley over the crossbar.
Cathal Heffernan, a representative of Republic of Ireland at under-19 level, went close to breaking the deadlock as Alfie Harrison's corner was flicked into the Irish defender's path before his close-range strike was pushed away by Tamworth goalkeeper Leon Phillips.
The 19-year-old centre-back, who joined Newcastle in August 2023 following his departure from AC Milan, went close minutes later after another dangerous corner by Harrison was headed down by McArthur before Alex Murphy directed the ball into Heffernan's path, who saw his first-time strike blocked inside a crowded penalty area.
In the second-half, Beck-Ray Enoru created an opportunity for the hosts, who knocked out League One side Huddersfield Town in the Emirates FA Cup last weekend as the Cameroonian's half volley following Shahar's headed clearance from a long throw-in flew wide of the target.
Newcastle's dominance and patience in possession paid off when, in the 63rd minute, the visitors took the lead as two substitutes combined, with Turner-Cooke's bending free-kick finding Donaldson inside the box before the Gateshead-born forward poked the ball beyond Phillips into the bottom left-hand corner.
Parkinson went close to recording a seventh goal of the 2024/25 season at under-21 level as the Durham-born teenager, who made his Premier League debut for his boyhood club against AFC Bournemouth in November 2023, latched onto Turner-Cooke's delightful long-range pass but could only steer the ball wide of the left-hand post.
James Huntley was unfortunate not to double the visitors' lead as the Ashington-born midfielder's ferocious drive from the edge of the box was palmed away by Phillips.
Newcastle found themselves on level terms in the 84th minute through Tshikuna's controversial equaliser. After the Newcastle backline believed to have gained a goal kick, Tamworth were instead awarded a corner before the set piece was cleared into Tshikuna's path, who fired an unstoppable volley into the top left-hand corner.
In the penalty shoot-out, Parkinson's confident penalty opened proceedings in the shoot-out but, despite Kieran Wallace firing wide for the hosts, Huntley was unable to capitalise after the 20-year-old's spot-kick was saved by Phillips, who guessed the correct way.
However, Turner-Cooke, Donaldson, Emerson, McArthur and Shahar all netted impressive attempt from 12 yards before Williams' drilled spot-kick struck the underside of the woodwork, resulting in an additional point for O'Carroll's side, gaining a third away win in their last five competitive outings in the process.
Newcastle United Under-21s: Aidan Harris, Leo Shahar, Cathal Heffernan (c), Charlie McArthur, Alex Murphy (Ellis Stanton 46), Travis Hernes, Anthony Munda (Josh Donaldson 54), Alfie Harrison (James Huntley 54), Trevan Sanusi (Jay Turner-Cooke 54), Garang Kuol (Johnny Emerson 68), Ben Parkinson.
Subs not used: Harry Powell, Will Anderson.
