Objective To measure the impact of prescription drug monitoring programs (PDMPs) on prescribing of opioid and nonopioid painkillers. Data Source 2010–2013 physician‐level Medicare Part D prescribing data released by the Centers for Medicare and Medicaid Services and Propublica. Study Design Using difference‐in‐differences models with physician‐level fixed effects, the study compares prescribing in states with and without PDMPs for opioid and nonopioid analgesics, oxycodone, hydrocodone, and opioids by controlled substances Schedules II–IV. Principal Findings Prescription drug monitoring programs were associated with a 5.2 percent decrease in days supply prescribed per physician for oxycodone in addition to smaller reductions for hydrocodone and opioids overall (2.8 percent and 2 percent, respectively) and a small increase in prescribing for Schedule IV opioids. PDMPs were not associated with changes for nonopioid analgesics or other opioids in Schedules II and III. The effects of PDMPs were negated in states where statutes explicitly did not require use of the PDMP. Conclusions Prescription drug monitoring programs have a modest effect targeted at the high‐profile drug oxycodone among the Medicare Part D population and an even smaller effect for hydrocodone and opioids in general. The findings suggest some substitution toward lower schedule opioids. Substantially addressing the widespread opioid abuse problem will require enhancing existing PDMPs or implementing new policies.