Opioid use among metastatic breast cancer (MBC) patients has not been well-studied. This study examined the trends and patterns of opioid use among working-age, privately insured patients diagnosed with MBC. Using MarketScan data, we identified female patients diagnosed with MBC in 2006-2015. We determined the proportion of patients who filled a prescription for an opioid and calculated days' supply and daily morphine milligram equivalents (MMEs) from 1 year prior to diagnosis till 1 year after. We assessed the trend in opioid use over the 10-year study period and examined opioid usage patterns after the diagnosis of MBC. Among 24,752 patients included, 11,579 (46.8%) had an opioid prescription within 1 year before diagnosis of MBC, and 20,416 (81.4%) had an opioid prescription within 1 year after diagnosis. The proportion of patients with opioid prescriptions after diagnosis was relatively stable from 2006 to 2015. However, both the median daily MME and median days' supply decreased over time with most of the decline from the subgroup of patients with prior prescription opioid use. Most patients received an opioid prescription in the first month after diagnosis (57.3%), dropping to approximately 20% from 3 to 12 months after diagnosis. Also, the median days' supply increased substantially during the year after diagnosis for patients who received opioids (from 7 to 19). Most women with MBC require opioid analgesia within the first month after diagnosis. Judicious, long-term management of pain after diagnosis of MBC will continue to be necessary for many patients.