Students with learning disabilities (LD), such as dyslexia, are at a greater risk of not completing their postsecondary education compared to their peers. Completion broadly and success more generally rest on how students navigate assessment experiences during postsecondary education. Generally, assessment is viewed as a controlling practice. From a self-determination theory (SDT) lens, highly controlling elements of schoolwork frustrate rather than satisfy students' basic psychological needs. Importantly, satisfaction, rather than frustration, supports intrinsic motivation and wellbeing. The current study examines the experiences of classroom assessment as satisfying or frustrating for students with dyslexia through an online methodology involving both Likert questions and written responses to structured open-ended questions. Overall, when students reported basic psychological need satisfaction, they likewise indicated that they received higher grades and felt more successful. From the open-ended data, we extracted three main themes and 12 sub-themes from the interviews: (a) student characteristics (including dyslexia, effort, prior knowledge, and emotions), (b) the role of others (including help, demeanor, structure, and choice), and (c) outcomes (including grades, knowledge and skills, reactions, and future impact). Taken together, when students experience classroom assessment in a way that supports their basic psychological needs, they experience better outcomes (e.g., high grades and perceived success) than when their basic psychological needs are frustrated. We discuss these results in terms of suggestions for instruction and assessment.