The loss of power on the Splendor forced nearly 4,500 passengers to endure a hot, four-day tow back to the port.
Many air conditioners, toilets and refrigerators stopped working, passengers said.
The Coast Guard detailed the crew's mistakes in a 51-page report on the fire that broke out on the cruise ship as it sailed from Long Beach to Mexico, the Los Angeles Times said.
When the fire alarm began going off, a crew member reset it, causing a 15-minute delay in the activation of an automatic fire-suppression system, the report indicated.
The report also criticizes the crew's unfamiliarity with the engine room, which made it difficult for the workers to find and extinguish the fire.
"We agree with the U.S. Coast Guard's conclusions surrounding fire detection and firefighting processes and took numerous actions throughout our fleet as a result," Carnival said in a statement.
Carnival also noted no injuries were reported as a result of the 2010 incident.