Employees of the watchdog organization, the Southern Poverty Law Center, are filing for union representation.
A supermajority of employees has requested representation by the Washington-Baltimore News Guild, Local 32035 of The News Guild-Communications Workers of America, AFL-CIO, the union announced this week.
"We ask SPLC's senior leaders to respect the desire of its dedicated employees to form a union and have a say in what the future of the Center looks like," the organizing committee said in a statement.
"Current leadership has committed itself to the task of changing SPLC's workplace culture. Collective bargaining ensures workers the opportunity to play a leading role in this transformation."
The move comes after upheaval that saw the departure of longtime leaders and the announcement of a review of workplace culture.
The organizing committee says it wants to form a strong union that lays a "foundation for a legacy of equal rights, respect and dignity for all workers, regardless of race, color, religion, sex, sexual orientation, gender identity, physical ability, and national origin."
In a letter to staff, Lecia Brooks, the SPLC's chief workplace transformation officer, said that management received the petition but suggested the group will wait on a formal vote to recognize the union.
Brooks wrote they "welcome an open election process" by employees on the decision to form a union.
The letter noted that the SPLC has "a long history of partnering with unions in our legal work."