Students' perceptions of assessment in higher education (HE) are critical, since such perceptions can enhance or diminish student motivation for learning. Despite this, research on students' perceptions of assessment in HE is scarce. To initiate a new agenda in this area, the present study explored Iranian doctoral students' (N = 16) perceptions of assessment and their emotional/behavioral reactions towards assessment. Qualitative data were collected and analyzed using a phenomenological approach. The overall findings indicated that students' perceptions of assessment: (a) predominantly centered on unethical issues, (b) evoked some negative emotional but not behavioral reactions towards such perceived unethical assessment, and (c) were mostly summative-oriented. Specifically, based on the findings, a tripartite, local model of assessment was generated highlighting that unethical assessment is relevant to assessment, instructional, and micro-political (power) issues. In the light of these findings, this study may add a new conceptualization of assessment ethics to the literature and highlights the inclusion of training courses on ethics principles across HE professional development programs in Iran and elsewhere.