The company confirmed PSN returned online in a tweet early Monday morning.
Sony says PSN and the Sony Entertainment Network were suffering outages following "an attempt to overwhelm our network with artificially high traffic." However, the company says users' personal information has not been accessed.
A group called Lizard Squad claims credit for the attack, as well as several others against Blizzard Entertainment, which develops World of Warcraft and Hearthstone, and League of Legends creators Riot Games.
The group used a distributed denial of service (DDOS) attack, which clogs a network or service so that it becomes unavailable to users.
The flight of Sony Online Entertainment chief John Smedley was diverted from San Diego to Phoenix after Lizard Squad sent a tweet to American Airlines claiming there were explosives on board. An American Airlines spokeswoman confirmed Flight 362 from Dallas/Fort Worth to San Diego was diverted to Phoenix "due to a security-related issue."
Smedley later confirmed the diverted flight in a later tweet.
PSN has been the target of hackers before. In 2011, the service was down for more than a month after it was compromised by hackers. The intrusion exposed personal data on 77 million users.
Sony says scheduled maintenance planned for Monday has been postponed in light of the attack.