To address the epidemic of opioid misuse and overdose, the New York City Department of Health and Mental Hygiene partnered with an expert panel of emergency medicine physicians to develop voluntary guidelines for judicious prescribing of opioids upon discharge from an emergency department. A qualitative evaluation of the guidelines was conducted using semistructured interviews with emergency department directors and providers. The guidelines were widely supported by respondents and cited as helpful in easing difficult negotiations with patients requesting opioids. Involvement of the expert panel in development of guidelines was particularly valuable in ensuring their credibility. Health departments should consider partnering with emergency physicians to promote the public health goal of judicious opioid prescribing.