Three days on from the late loss to Brazil, the absentee-hit Euro 2020 runners-up faced another high-level test as the side third in FIFA’s world rankings hosted the team in fourth.
England were heading for another Wembley defeat after Youri Tielemans punished first-half errors either side of Ivan Toney’s penalty, only for Bellingham to secure a 2-2 draw in stoppage time.
Toney did well on his first start, as did fellow full debutants Ezri Konsa and, in particular, 18-year-old Kobbie Mainoo in the final friendly before Southgate names an expanded Euros squad on May 21.
The England boss has plenty of food for thought after a night of promise and problems, which started with John Stones limping off and Tielemans capitalising on a Jordan Pickford error in a nightmare first 11 minutes.
England rallied and quickly levelled as Toney converted the penalty he won, before Jarrod Bowen saw a first international goal ruled out for offside.
Southgate’s side continued strongly, but Lewis Dunk’s failed attempt to cut out a long ball allowed Romelu Lukaku to superbly cross for Tielemans to head Belgium back ahead.
England responded impressively after the break but looked set to fall short until Bellingham’s stoppage-time strike.
Southgate’s delight was clear at the end of a night that started with Stones limping off, just as Manchester City team-mate Kyle Walker had done against Brazil.
That bad start got worse as England conceded an avoidable opener.
Pickford, normally so reliable with his kicking, saw a low pass forwards cut out by Everton team-mate Amadou Onana, with Tielemans smartly lasering low past the panicked goalkeeper.
The embarrassed England number one’s relief was palpable when Toney levelled in the 17th minute.
Mainoo showed great awareness and confidence to play into Bellingham, whose ball through to the Brentford striker led to a clumsy Jan Vertonghen challenge.
Referee Sebastian Gishamer pointed to the spot and Toney superbly sent Matz Sels the wrong way.
Belgium responded as Jeremy Doku cut past substitute Joe Gomez to test Pickford, but England were looking far more threatening than they had against Brazil.
Bellingham saw a cross brilliantly cleared and a Phil Foden corner was nodded on by Dunk for Bowen to glance in a header, only for the VAR to rule out his first England goal for offside.
Bellingham inexplicably blazed over from close range as impressive Mainoo won the ball deep in Belgium territory – a big miss the visitors were punished for in the 36th minute.
Dunk went to ground trying to deal with a diagonal ball forward from Tielemans, but the centre-back failed in his attempt to stop Lukaku reaching it.
The Belgium striker sent over an exquisite cross with the outside of his boot, which Tielemans met with a diving header. A sucker punch that gave Belgium a half-time lead.
England returned from the break without names on the back of their shirts as part of a campaign to raise awareness of dementia in Tuesday’s Alzheimer’s Society International.
Southgate’s side pushed to equalise again as the rain continued to tumble, with Foden following a great run with a ball out wide for Toney to force Sels into a fine save.
The Nottingham Forest goalkeeper was relieved to see Bellingham head wide as England pushed against a side capable of breaking at speed.
Neat play ended with Bowen hitting a first-time shot at Belgium’s goalkeeper, with Sels doing well to stop Mainoo driving home.
The Manchester United midfielder received a great ovation and hug from Southgate after being taken off in the 74th minute, with Bowen doing well and Foden dragging across the face of goal as England kept pushing.
Belgium substitute Dodi Lukebakio had a chance to punish the hosts in stoppage time, when England would finally find a way.
Substitute James Maddison played back for Bellingham to take a touch and lash home to the delight of those left at Wembley.