Objective The sudden outbreak of COVID-19 has caused major health problems, including anxiety in cancer patients worldwide. Spiritual health and mindfulness are considered as factors affecting anxiety. This study addressed the relationship between COVID-19 anxiety, spiritual health and mindfulness in patients with cancer. Methods One hundred and eighty-four cancer patients participated in this cross-sectional study. The data were collected with convenience sampling method from two oncology centers from 15 June to 15 July 2020 in the southeast Iran. Patients completed the Demographic and Clinical Characteristics Form, Corona Disease Anxiety Scale (CDAS), The Freiburg Mindfulness inventory-Short Form (FMI-SF) and Spiritual Health Scale. Results According to the psychological symptom subscale (CDAS), 61.4% of the participants had moderate to severe anxiety. According to the physical symptom subscale, 38% of the participants had moderate to severe anxiety. No significant association was found between corona disease anxiety and mindfulness/spiritual health (p>0.05). Conclusion The results of this study showed high levels of mental and physical anxiety and worries about COVID-19 disease in cancer patients, which led to challenges in their lives. It is necessary to review and implement effective interventions in future studies to prevent anxiety and its consequences in cancer patients.