The company acknowledged the expanded inquiry in a Securities and Exchange Commission filing that accompanied its third-quarter financial results, which showed lower sales than analysts had expected.
Walmart had previously reported that the audit committee of its board was examining possible violations of the Foreign Corrupt Practices Act in Mexico.
"Inquiries or investigations regarding allegations of potential FCPA violations have been commenced in a number of foreign markets where we operate, including but not limited to Brazil, China and India," the company said in its regulatory filing.
Walmart's shares were down about 4 percent in early trading.
The New York Times reported in April that seven years ago, Walmart had found credible evidence that its Mexican subsidiary had paid bribes, a violation of the Foreign Corrupt Practices Act, and that an internal investigation into the matter had been suppressed by executives at the company's Arkansas headquarters.
The company has had teams of lawyers looking into the Mexico issue and potential violations of the law elsewhere. In the filing, the company said it had "identified or been made aware of" other potential violations.
"When such allegations are reported or identified, the Audit Committee and the company, together with their third party advisers, conduct inquiries and when warranted based on those inquiries, open investigations," it said.
Walmart suggested in May that the investigation had broadened, but Thursday's filing with the SEC was the first time it has specified the other countries it is looking into.
The SEC and the Justice Department have opened investigations into the Mexico matter, and Walmart said it is cooperating with them. Charles M. Holley Jr., Walmart's chief financial officer, declined to comment Thursday on whether the agencies are looking into countries other than Mexico.
"As you would expect with these matters, because they're under review, it would be inappropriate for me to comment on specific matters until the investigation is concluded," he said.
The company spent $99 million in the first nine months of the year in expenses related to the matter, like complying with subpoenas, defending itself against shareholder lawsuits and conducting the review.
The company exceeded third-quarter earnings expectations by a penny a share, reporting profit of $3.63 billion, or $1.08 a share, compared with $3.33 billion, or 96 cents a share, in the period a year earlier.
But its revenue missed analysts' predictions. It rose 3.4 percent, to $113.2 billion, compared with expectations of $114.96 billion. The company said that without currency fluctuation, sales would have been $114.9 billion. Sales at stores open at least a year in the United States grew 1.5 percent, a little less than analysts had projected.
In recorded statements, Walmart executives indicated even middle-income consumers were under increasing pressure. At the company's Sam's Club division, a warehouse club that attracts a higher-income shopper than Walmart stores, shoppers are starting to swap out steak for pork, for instance, because it is cheaper.
The company said Hurricane Sandy had cost it about $35 million in damaged inventory and cleanup costs but had not significantly affected its ability to get merchandise to stores.