While there is technically no minimum number of people needed for a class action, it is difficult (although not unheard of) to get a case with fewer than 40 individuals certified.
It only takes one person to file a class action lawsuit, but in order for a class action to proceed, a judge must first certify the class. Judges exercise some discretion when making the certification decision, but they do so within the context of Rule 23 of the Federal Rules of Procedure, which says that a class action is appropriate when “the class is so numerous that joinder of all members is impracticable.”
But so-called “numerosity” is not the only class action prerequisite. Rule 23 also states that there must be “questions of law or fact common to the class” (commonality); that the claims of those who file the class action on behalf of others are typical of the claims of the class (typicality); and that those filing the lawsuit “will fairly and adequately protect the interests of the class” (adequacy of representation).
When plaintiffs’ lawyers move to certify the class action, a judge will consider the numerosity of the class. Yet supposing that the judge deems the number of class members to be adequate, if the other requirements of commonality, typicality, and adequacy of representation are not met, the class won’t be certified.