The teenager was approached by a group of men before they chased him into the takeaway on Rookery Road at about 3pm on Saturday.
Police were later filmed at the Big Saj fish and chip shop opposite Onibury Road.
The boy's injuries are not believed to be life threatening, West Midlands Police said.
A spokesman for the force said: "We’re investigating after a boy aged 14 was stabbed on Rookery Road, Handsworth, at around 3pm yesterday.
"He was approached by a number of men before they chased him into a takeaway and stabbed him twice.
"His injuries are not believed to be life changing or life threatening.
"CCTV and house-to-house enquiries are under way.
"Anyone with information has been asked to get in touch via Live Chat at west-midlands.police.uk, quoting 20BW/239621Y/20.
"Alternatively, contact us on 101 or Crimestoppers anonymously on 0800 555 111."
The attack is the latest of many violent incidents to take place on Rookery Road, which runs from the A41 to Oxhill Road.