After remaining stable from 2010 to 2014, the rate of cocaine-involved overdose death increased sharply from 2015 to 2016. This study aims to determine the contribution of opioids, and fentanyl in particular, to the increase in cocaine-involved overdose death from 2015 to 2016. Using New York City death certificate data linked to medical examiner toxicology data, we identified all overdose deaths where post-mortem toxicology results were positive for cocaine from 2010 to 2016. We analyzed cocaine-involved overdose deaths by co-occurring substances. Age-adjusted rates per 100,000 residents were calculated for 6-month intervals from 2010 to 2016. Data suggest that increased deaths involving opioids, specifically fentanyl, accounted for most of the increase in cocaine-involved deaths from 2015 to 2016.