Background <p>The increasing cancer incidence in countries found in the Middle East is associated with challenges that impact the family members (family caregivers) caring for the affected patients. In countries such as Oman, with recently established cancer care systems, there are no programs or studies to address the needs of family caregivers (FCs).</p> Purpose <p>To investigate the unmet needs and their relationship with the emotional well-being of FCs of adult patients with cancer in Oman.</p> Methods <p>A descriptive cross-sectional design was used to collect data from 198 FCs and patients with cancer in Oman. Data were collected using a self-administered questionnaire comprised of the Needs Assessment Family Caregiver-Cancer scale, the Hospital Anxiety and Depression Scale, and the Spiritual Well-being scale.</p> Results <p>The highest level of unfulfilled needs was in aspects such as medical care, patient symptoms, emotional distress, and caregiver self-care. The FCs who were female, young, unemployed, and caring for patients with high pain levels reported more unmet needs. Most FCs reported moderate religious and existential well-being and moderate anxiety and depression symptoms. A high level of unfulfilled needs was associated with decreasing spiritual well-being (<i>p</i> ≤ 0.05), but not with anxiety and depressive symptoms.</p> Conclusion <p>Family caregivers of patients with cancer in Oman experience unmet needs that could affect the health outcomes of the dyad. Cancer care services in Oman should consider integrating holistic and supportive care services for both the patients and their FCs to address the unmet needs and enhance health outcomes.</p>