Ivor Smith was sacked for gross misconduct after helping a customer with change at the firm's Parkhead branch in Glasgow on 15 August 2014.
An employment judge has now ruled that he was unfairly dismissed and awarded Mr Smith, from East Kilbride, £4,877.
His son Alan said the whole process had left his father "shattered".
The employment tribunal in Glasgow heard that Mr Smith had worked at the store for 12 years.
He was working on a checkout when a customer asked him for change of £200 in £1 coins.
War veteran Mr Smith, who fought in the Malayan conflict of the 1950s and 60s, was said to have kept his till open while money was counted at it.
The 83-year-old said he was later marched out of the shop "like a criminal" after being accused of causing a "serious breach of security".
The tribunal heard from branch trading manager Euan Wilson, who said he had to sack Mr Smith for gross misconduct.
This was after he claimed the cameras showed the customer putting his hand into the till on two occasions.
Mr Wilson told the hearing: "My view was that this was a serious breach of security. A tender transaction should not take that long.
"He gave customers access to the till."
Mr Smith, who had received commendations for his commitment to the company, insisted the customer never touched any money.
He told the tribunal: "I always said I would work until I was 90 and I would have carried on until my health got bad. I just don't understand being dismissed for a misdemeanour."
Following the tribunal decision of unfair dismissal, Mr Smith's son Alan said his father's main objective was clearing his name.
He added: "From being a confident man of his age, the humiliation of that, being ushered out the building left his fellow employees with the impression that money might have gone missing - and that was the rumour.
"It really did shatter him and that's what made us decide to fight it, it was never about the money, it was just about clearing his name because he has gone through quite a lot of anxiety over it."
An 83-year-old man who was sacked by B&Q for leaving his till open for three-and-a-half minutes has won his case for unfair dismissal.