In their motion to join a federal lawsuit, the 12 men allege the anti-gang officers who carried out the illegal strip and cavity searches engaged in a "racially motivated conspiracy" to deprive black residents of their rights.
The 12 men are African American. All of the accused officers are white.
The Milwaukee Journal Sentinel reports a total of 47 people have already sued the city and police department over the searches, which happened from 2008 through 2012.
Police spokesman Mark Stanmeyer has said the department does not comment on pending litigation.