The unions, which represent some 14,000 Disneyland Resort employees, have been in negotiations with Disney over wage increases and other benefits since April.
Talks have stalled and tensions have grown as some employees contend Disney has engaged in anti-union practices.
Ninety-nine percent of members voted in favor of the strike authorization, according to a union statement.
It allows union leaders to decide when to call the strike, as well as its duration and terms.
This week, Disney said it was "committed" to continuing negotiations scheduled for Monday and Tuesday.
If the talks go ahead as planned, the strike authorization vote gives union members new leverage in negotiations.
"A strike is always a last resort for workers, but this strong vote shows that cast members across Disneyland are ready and willing to do what it takes to stand up to Disney’s unfair labor practices and get the contract they deserve," the Disney Workers Rising Bargaining Committee said in the statement.
"Today's overwhelming unfair labor practice strike authorization vote sends a clear message to the company: 'we are stronger together and will not be divided by scare tactics'".
After last year's writers and actors strike paralyzed Hollywood, another major labor movement within Disney would be historic.
Employees at its California theme parks have not gone on strike since 1984, according to the Los Angeles Times.
On Wednesday, hundreds of Disneyland employees, also known as "cast members," gathered for a protest in a parking lot outside the park in Anaheim, a suburb of Los Angeles.
The employees complained of low wages and intimidation used by managers, prompting a complaint filed with the National Labor Relations Board.
The union claims that over 500 employees have been reprimanded, threatened or warned about disciplinary action for wearing a union pin, which depicts a Mickey Mouse glove raised in the shape of a fist.
"Last week, I saw a manager telling one of the cast members to remove her badge," Disneyland employee Ginny Cristales, 44, told AFP over the phone. "He told her that it will be on her record card... She was stressed and scared."
Cristales has worked at Disneyland for the past five years, earning around $2,800 a month -- which is not enough to cover the rent for her and her four children.
"We deserve fair wages," Cristales said. "A strike is our last resort, that we're not wanting to do. But if Disney doesn't comply and give us what we need, then we're all ready."
