Arnold & Porter is one of 64 law firms to achieve Mansfield Certification after completing the twelve-month Mansfield Rule Certification 2.0 program, which measures how law firms affirmatively consider women, minority lawyers, and LGBTQ+ lawyers for significant leadership roles. This is the second year in a row that Arnold & Porter has achieved this certification. Arnold & Porter also maintained its Mansfield Certification Plus rating, a status that recognizes firms with at least 30 percent of women or diverse lawyers in leading roles.

The Mansfield Rule, named for the first woman admitted to the practice of law in the United States, is modeled after the NFL's Rooney Rule, which requires all NFL teams to interview at least one minority candidate for head coach and general manager vacancies. The Mansfield Rule aims to similarly diversify the legal space. For participating firms, the Mansfield Rule 2.0 requires that women, minority attorneys, and LGBTQ+ attorneys make up 30 percent of the candidate pool for leadership positions, equity partner promotions, and certain lateral hires.

The Mansfield Rule stems from the 2016 Women In Law Hackathon, a competition hosted by Diversity Lab in collaboration with Bloomberg Law and Stanford Law School intended to generate ideas for boosting "the retention and advancement of experienced women in law firms." Diversity Lab already launched its Mansfield Rule 3.0 program, with Arnold & Porter as one of the participating firms.

Diversity and inclusion are core values at Arnold & Porter. The firm is committed to cultivating an inclusive environment where everyone is supported and accorded dignity and respect. The firm has recently been named to Working Mother's 'Best Law Firms for Women' List and the Human Rights Campaign Foundation's Best Place to Work for LGBTQ Equality.