Opioids have long been used for clinical pain management, but also have addictive properties that have contributed to the ongoing opioid epidemic. While opioid activation of opioid receptors is well known to contribute to reward and reinforcement, data now also suggest that opioid activation of immune signaling via toll-like receptor 4 (TLR4) may also play a role in addiction-like processes. TLR4 expression is enriched in immune cells in peripheral organs and blood and in the nervous system is primarily expressed in microglia, the resident immune cells of the central nervous system. In peripheral immune cells, morphine is repeatedly shown to decreases immune activation and phagocytosis in vivo and in vitro. Phagocytosis is an important immune effector that serves to clear damage, debris, and infection. Unlike peripheral immune cells, the effect of morphine on microglia is less well studied. Morphine is reported to both increase and decrease microglial phagocytosis. Several different factors contribute to microglial phagocytic activity, including sex, region, and local microglial density. We hypothesized that morphine increases phagocytic activity in microglia, but in a density-, dose-, region-, and sex-dependent manner ex vivo. To test this, we isolated microglia from adult male and female rat cortex and striatum and plated them ex vivo at a relatively low or high density. Microglia were incubated with neutral fluorescent microbeads to stimulate phagocytosis in the presence of one of four morphine doses. We found that brain region of origination and plating density, but not sex, impacted microglial phagocytosis at baseline. These heterogenous properties further diverge when morphine is applied causing emergence of effects not observed at baseline, maintenance of some baseline effects, and disappearance of effects observed at baseline. Further work is necessary to identify the precise interactions and signaling that is dominant in different sex, region, and density contexts to better understand the complex effects of opioids on microglial immunoregulation.