Perceived discrimination has been found to be a common acculturative stressor among migrants negatively affecting their psychological acculturation process. Yet, a comprehensive review that focuses on how perceived discrimination is conceptualized and operationalized in the acculturation context is still missing. Furthermore, it is still unclear whether subtle and blatant forms of discrimination have been considered and compared in their effects in the acculturation literature, albeit some research suggests that the distinction between these two forms of discrimination is relevant and should be considered. Following the guidelines of the Joanna Briggs Institute, the present scoping review aimed to provide a systematic map of how perceived discrimination has been studied in the literature on first-generation adult immigrants’ psychological acculturation. A comprehensive search was executed in three databases (EBSCO, Scopus, and Web of Science), and 2,872 relevant sources were identified. A total of 143 studies were included after screening abstracts and full texts. A systematic coding scheme was then applied to all included articles. Results showed that 80% of the studies were cross-sectional and/or considered discrimination as a predictor of psychological outcomes, while other variables, for example, acculturation orientations and identity constructs, have been much less studied. Perceived discrimination was measured with over 50 different scales, yet only 10% of the studies made a clear conceptual difference between subtle and blatant discrimination. Moreover, the operationalization of these two forms of discrimination was often ambiguous. The present review identifies important knowledge gaps in the acculturation literature and draws recommendations for future research.