A "spiritual message of goodwill" was found in a tree near the front gates of Disneyland on Saturday, hours after the item was reported as suspicious and prompted the park's lockdown.
Police said the object was a peaceful scroll intended for park guests.
The park had been shut down for hours out of an abundance of caution while the bomb squad investigated.
A similar incident prompted the park's temporary closure last year when officials reported seeing a cylindrical object in Downtown Disney.
That object turned out to be not a bomb, but the hidden loot of a harmless game.
Police initially thought the item found Saturday was part of the same game, a high tech hide and seek adventure called geocaching in which people use global positioning systems to find containers that contain toys and trinkets.
"Initially that was one of the things that was at the forefront of our minds was geocaching," said Anaheim police Sgt. Bob Dunn, a department spokesman.
The all clear was given after the person responsible for the message called police to let them know it was a peaceful note, police said.
Suzi Brown, a Disneyland spokeswoman, said the park was shut down out of an "abundance of caution."
"This is not the first time," Brown said. "Unfortunately, people can't do that. We take it seriously."
The park reopened about 11 a.m.
As a courtesy, officials said they'd keep both Disneyland and California Adventure open an hour later than normal Saturday due to the inconvenience.
Disneyland would close at 1 a.m. and California Adventure would close at 10 p.m.
The park had been set to open at 8 a.m. Saturday. But no one was allowed in or let out of the Anaheim theme park after security officers found a suspicious package during a pre-opening walk through at 7 a.m.
Twitter lit up with reactions to the shutdown.
Phil Balanga, whose Twitter handle is @OC_Phil, said:
"Guests annoyed and angry because they can't get into the park due to bomb threat. I think their priorities are askew just a bit."
Maya, whose Twitter handle is @EyeOfMara, said:
"To the foolish mortal who left an unattended "bag" outside the realm of Disneyland this morning... DOOMED for trying to ruin MY birthday!"
Tom Bricker, who goes by the Twitter handle, @wdwfigment, said:
"Bomb threat closes #disneyland. "awesome" way to start the day..."
"Since #Disneyland is on a lockdown due to unidentified object in Esplanade, guests inside are enjoying an empty park with walk-ons to rides."