An Alabama man filed suit in California, accusing the company of, "not taking reasonable care to protect, encrypt and secure the private and sensitive data of its users."
Sony is telling PlayStation users that it had encrypted the credit card data that hackers may have stolen, reducing the chances that thieves could have used the information.
It did not say how strong the encryption was, and it's possible for hackers to decipher files that are weakly encrypted.
He also says Sony took too long to notify him and other customers that their information may have been compromised.
The lawsuit is seeking monetary compensation and free credit monitoring.
The Associated Press contributed to this report.