A problem with one of the property's transformers triggered the outage at the Anaheim park, cutting power to about one dozen rides altogether.
"All of Toontown and parts of Fantasyland are affected by the outage", Twitter user Sarah Mansoor wrote.
Disney officials said a glitch with an electrical transformer caused the power to go down at the Anaheim amusement park's Toontown and Fantasyland.
Geoff Feinberg told CNN he and his family were halfway through the "It's a Small World" ride when the power shutdown.
"We sat there for about 25 minutes in the dark", he was quoted as saying by the New York Daily News. You're just sort of sitting in a boat.
Other guests noted that they were unable to obtain refunds, and said the park's crowds were unhappy.
Power was restored to most of the area by noon, although park officials did not give estimates as to when all the rides would be fully functioning.
The power outage comes amid Disneyland's busy holiday season.
Earlier in the day, the Disneyland App tweeted that it would be "very busy today".