Workplace diversity and inclusion (D & I) practices today are based to a great extent on unevaluated experience and intuition rather than empirical evidence. Would voluntary professional practice standards in this field help to raise the level of current and future practice? Or would they be premature? If developed under 4 principles we describe, we predict the former. However, this positive outcome will also require industrial and organizational (I–O) psychologists to join their D & I colleagues in expanding research on D & I practices, strengthening the skills of D & I practitioners, assisting employers to avoid self-incrimination, and enhancing employer commitment to D & I itself. I–O psychologists should also be aware of other implications of D & I practice standards for their work.