Objective: This study assessed trends in days’ supply for opioid prescriptions filled by adolescents with commercial insurance and Medicaid. Methods: IBM MarketScan commercial and Medicaid pharmacy claims data were used to measure days’ supply among adolescents (2005–2016) and to determine whether there were differences between patients with commercial insurance or Medicaid coverage. Results: The 2–3 days’ supply decreased from 50.5% (2005) to 36.7% of fills (2016), while 4–5 days’ supply increased from 30.2% to 37.7%. Fills of 6–7 and 8–15 days increased slightly. Fills of over 30 days remained near 0.0%, and one-day fills remained at 1.0–2.0% until 2016, when they increased to 3.6% Conclusions: For adolescents, fills of prescription opioids generally exceeded three days. Efforts to reduce opioid prescribing through guidelines, prescription drug monitoring programs, and limits on days’ supply do not appear to have affected prescribing for adolescents as much as desired.