NCAA Accountability Act of 2021 This bill establishes due process and notice requirements for the investigations carried out by certain intercollegiate athletic associations and related organizations. Specifically, the requirements apply to interstate athletic associations, conferences, or other organizations with authority over intercollegiate athletics or that administer intercollegiate athletics and that have at least 900 member institutions. Such organizations must establish and administer due process requirements for the investigation of any member institution, student athlete enrolled in such member institution, or other individual for infractions of the athletic association's bylaws or failure to meet the conditions and obligations of membership. The Department of Justice must establish procedures for (1) individuals and entities to file complaints, (2) the investigation of complaints that have a substantial probability of validity, and (3) the investigation of other violations of this bill.