Mitochondrial diseases (MtD) are amongst the most common inherited metabolic disorders, affecting approximately 1 in 5,000 individuals. The MtD diagnostic journey is often long and arduous due to the clinical and genetic heterogeneity of these conditions. Previous research on rare diseases shows that education, emotional support, and access to services are important to those navigating the diagnostic process. However, no studies to date have collectively assessed these needs specifically for MtD. Therefore, this study aimed to describe the diagnostic experience and explore in-depth the informational, psychological, and social needs of individuals and parents/caregivers of children with confirmed MtD. This study followed an embedded mixed-methods design, where participants completed surveys to detail their diagnostic journey and semi-structured interviews to delve deeper into these experiences. Seventeen affected individuals and parents/caregivers completed a survey, and twelve of these participants completed an interview. The diagnostic journey was conceptualized to unfold in stages, with the number of specialists consulted and time to diagnosis being less than initially anticipated. Providers, the Internet, and personal networks were key sources of information and support, while support organizations and groups were found to be the least accessed. Participants described needing more information and support throughout the diagnostic process. Information and support resources for MtD understandably became more available upon diagnosis. However, the general lack of knowledge surrounding MtD meant uncertainty remained post-diagnosis. Psychological consequences of the journey were significant and heavily intertwined with the desire for an answer. Social needs extended beyond the medical setting and were systematically unmet. Overall, participant needs evolved throughout the diagnostic journey and continued to change post-diagnosis. Foundational to the experiences and needs identified was the patient-provider relationship, mainly with genetics and neurology providers, which played a central role in how the journey was remembered and the extent to which participants felt supported. This study describes the complexities of the MtD diagnostic journey and highlights gaps in informational, psychological, and social supports. To improve the provision of MtD care, participant-driven recommendations focusing on assessment of needs and meaningful inclusion of patients and families in discussion and decision-making are presented.