Pret A Manger will provide full ingredient labelling on freshly made food after a 15-year-old girl died following an allergic reaction to a baguette.
Natasha Ednan-Laperouse died in 2016 after suffering a reaction to sesame seeds on a Pret baguette.
The fact that the Pret baguette contained sesame was not declared on the packet.
A coroner said the chain had failed to address the seriousness of food allergies, with the teenager's father Nadim Ednan-Laperouse accusing the company of a "complete dereliction of duty".
Now, Pret has announced that full ingredient labelling will be introduced to all products that are freshly made in its shop kitchens.
The firm says it will begin trialling the move from next month and plans to roll this out to all UK shops as quickly as possible.
Pret chief executive Clive Schlee said: "I want to say again how deeply sorry we are for the loss of Natasha.
"I said we would learn from this tragedy and ensure meaningful changes happen.
"I hope these measures set us on course to drive change in the industry so people with allergies are as protected and informed as possible.
"Nothing is more important to Pret right now."
Natasha, from Fulham, southwest London, collapsed on board a flight in July 2016 after eating an artichoke, olive and tapenade baguette she had bought at a Pret outlet in Heathrow airport.
Her family has called for a change in the law on food labelling to save lives.
At last week's inquest the coroner, Dr Sean Cummings, said Pret had relied on stickers, which urge customers to ask staff or check the Pret website, to provide information on allergens in their products.
Natasha had checked the packet before eating the baguette.
Dr Cummings said: "There was no specific allergen information on the baguette packaging or on the (food display cabinet) and Natasha was reassured by that."
The coroner said he would send a report to Environment Secretary Michael Gove concerning whether large businesses should be able to benefit from regulation five of the Food Information Regulations.
That allows for incomplete labelling of food products - not requiring identification of allergens in bold labelling on the packet.
Mr Gove said his department was currently reviewing its "approach to food labelling to give consumers more information" and stood ready to take "appropriate action".
In an interview with Sky News this week, Natasha's father called on politicians to "take heed and really do something about it".
"Every hour that goes past when there are not food labels with the allergens on the sandwich, someone else is at risk of dying or even having life-changing injuries as the result of a terrible anaphylactic reaction," he said.
"It's unthinkable that right now all sandwich shops haven't shut momentarily to get on and do something and do right by the public."