Objective: The primary goal of the study was to assess the efficacy of mindfulness-based meditation therapy on anxiety, depression, and spiritual well-being of Japanese patients undergoing anticancer treatment. A secondary goal was to assess the relationships among anxiety, depression, spiritual well-being, growth, appreciation, pain, and symptoms.Methods: The subjects were 28 patients who were receiving anticancer treatment. The subjects participated in two sessions of mindfulness-based meditation therapy, including breathing, yoga movement and meditation. Each patient was taught the program in the first session, then exercised at home with a CD, and subsequently met the interviewer in a second session after 2 weeks. Primary physicians recruited the patients and interviews were conducted individually by nurses or psychologists with training in the program. Patients completed preintervention and postintervention questionnaires on anxiety and depression (Hospital Anxiety and Depression Scale [HADS]), spiritual well-being (Functional Assessment of Chronic Illness Therapy-Spiritual [FACIT-Sp]), and appreciation, growth, pain, and symptoms. Results: HADS scores significantly decreased from 12 ± 5.3 to 8.6 ± 6.3 (p = 0.004) after the intervention, and FACIT-Sp increased from 32 ± 6.5 to 33 ± 6.9 (p = 0.69), but the change was not significant. There were significant associations between FACIT-Sp and HADS (r = −0.78, p = 000), FACIT-Sp and growth (r = −0.35, p = 0.04), FACIT-Sp and pain (r = −0.41, p = 0.02), and growth and appreciation (r = 0.45, p = 0.009). Conclusions: Mindfulness-based meditation therapy may be effective for anxiety and depression in Japanese cancer patients, and spiritual well-being is related to anxiety and depression, growth, and pain. The negative correlation of spirituality with growth differs from the results of previous studies and the mechanism of this effect needs to be investigated further.