Selective laser melting (SLM) is an additive manufacturing (AM) technique used to fabricate patient-specific orthopaedic implants out of highly corrosion resistant alloys such as cobalt–chromium–molybdenum (CoCrMo). Some of the challenges of using AM include parts that are susceptible to porosity, material anisotropy and high residual stresses, which degrade the mechanical properties of the components. However, these issues can be resolved through hot isostatic pressing (HIP). This research aims to investigate the effects of HIP on the corrosion behavior of additive manufactured CoCrMo in phosphate buffered saline (PBS), which is used as a simulated human body fluid, in both normal and inflammatory conditions. An increase in temperature, decrease in pH and introduction of a reactive oxygen species are all characteristics of inflammatory conditions. All of these changes result in an increase in the corrosion rate for both the as-processed additive manufactured and hot isostatic pressed samples. The results of this study also show that the as-processed additive manufactured CoCrMo shows elemental microsegregation, specifically that of Cr. This segregation results in areas that are depleted of Cr, which are then prone to corrosive attacks. HIP reduces the microsegregation in the additive manufactured material, thus increasing the availability of the alloying elements, Cr and Mo, to create a protective passive film which contributes to a higher corrosion resistance as opposed to as-processed CoCrMo in both normal and inflammatory conditions.