The bargain store and other huge chains, including Tesco, Amazon and John Lewis, have agreed to make it more difficult to buy blades in their stores.
Gulsen Alkan started a petition - following the killing of her art dealer husband Justin Skrebowski - encouraging retailers to agree formal measures in the hope of preventing others enduring the same tragic fate.
Home Secretary Theresa May questioned why cigarettes should be kept out of sight in shops but not knives.
More than 52,000 people pledged their support within a month, prompting the UK’s top chains, including Asda, Sainsbury’s, Lidl, Argos and Morrison’s, to take action.
Gulsen, of north Oxford, said: “Throughout this dreadful time I have not wanted revenge but rather the certain knowledge that no family should ever have to go through what my family has gone through.”
The agreement, which includes a crackdown on knife sales to under 18s and changes in the way blades are displayed, follows talks held last week between major retailers and the Home Secretary.
It increases focus on age verification checks for knife sales in-store, or if ordered online, at point of collection or delivery and commits retailers to regular staff training.
The Home Secretary said: “Knife crime has a devastating impact on victims, families and communities, and I am determined to do all I can to prevent it.
“Retailers have a vital role to play in this fight and I welcome today’s commitment. Knives have no place on our streets.”
Last week she also banned the sale of large serrated blades called ‘zombie knives’ in a bid to slash knife crime.
The new agreement will see retailers:
Apply the same age restriction policies they do to alcohol, such as think 21 or challenge 25, to ensure knives to not fall into the hands of under-18s.
Ensure knives are displayed and packaged securely, taking “practical and proportionate action to restrict accessibility and avoid immediate use, reduce the possibility of injury, and prevent theft”
Train all staff who will deliver, sell or approve the sale of knives, with refresher courses at least once a year