Office workers have stopped printing emails, are taking off-peak trains and are using less of the company's free coffee. Employees are also encouraged to submit money-saving suggestions.
Asda estimates the scheme, if successful, will save more than £60m a year.
One member of staff said even CEO Andy Bond was getting in on the action.
"Andy Bond noticed the dossiers prepared for the directors' meeting were being printed in colour," he said. "So he switched it to black and white, which we think will save about £2,000 a year. Not many CEOs of multi-billion pound businesses will brag about saving a few grand - that's how relentless our cost-cutting culture is."