Part-Time Worker Bill of Rights Act of 2020 This bill modifies various employment, leave, and pension rules with respect to part-time workers. Specifically, the bill removes the requirement that employees work a minimum number of hours during the preceding 12-month period before becoming eligible for family and medical leave. The bill also sets the maximum length of service on which employers may condition the eligibility of part-time employees for a qualified pension plan (e.g., 401(k) retirement plan). Except as required by an applicable collective bargaining agreement, such service requirement may be no longer than two consecutive 12-month periods of at least 500 hours of service for part-time employees who have reached the age of 21 by the end of such period. The bill further prohibits employers from setting disparate terms of employment or working conditions for part-time employees, including with respect to compensation, notice of work hours, and promotion opportunities, among others. Additionally, the bill requires large employers to offer available, qualified part-time employees additional work hours before hiring new employees for such hours. Among other enforcement methods, employers must maintain three years of certain records related to the requirements of this bill. The bill also provides a private right of action for employees to enforce the nondiscrimination requirements of this bill.