The company said thieves may have stolen credit and debit card information from customers and made unauthorized charges over the holiday season.
Only people who made purchases at Neiman Marcus stores are at risk - not those who bought things online.
Neiman Marcus spokeswoman Ginger Reeder said that the retailer had been notified in mid-December by its credit card processor about the issue. On Jan. 1, a forensics firm confirmed evidence that the retailer was a victim of a criminal cyber-security intrusion and that some customers' cards were possibly compromised as a result.
Reeder would not say how many customers were affected, but did say the merchant was notifying customers whose cards it knew were used fraudulently.
She also said the company is working with the Secret Service.
The revelations come as Target disclosed Friday that its massive data theft was significantly more extensive and affected millions more shoppers than the company announced in December. The nation's second largest discounter said hackers stole personal information - including names, phone numbers, email and mailing addresses - from as many as 70 million customers as part of a data breach it discovered last month.
The Associated Press contributed to this report.