This mixed methods study examined the association between the frequency of five lifestyle-related complementary and alternative medicine (CAM) practices and perceived quality of life (QOL) and stress among patients in Japan diagnosed with chronic disease, and also examined why patients decided to receive Okada purifying therapy [(OPT) biofield therapy]. Data from 1,190 patients were analyzed using bivariate and multiple regression analysis, followed by analysis of one-on-one in-depth interviews conducted among 25 patients on reasons why patients decided to practice OPT. Grounded theory methodology was used to analyze transcribed interview data. Results of multiple regression analysis indicated that engaging in arts and cultural activities and exercise was associated with a decrease in perceived stress, while arts and cultural activities, exercise, consumption of organic (additive-free) food, and practice of OPT were associated with increased QOL. Gender weakly moderated the effects of arts and cultural activities on stress but not on QOL, and gender did not have any moderating effects on the association of OPT with either stress or QOL. One theme, five clusters, and 13 categories emerged from the qualitative analysis. Feelings of desperation due to unrelieved symptoms of disease seemed to be the principal reason for most patients’ practice of OPT. Other reasons were perception of the limits of conventional medicine in being able to treat patients’ disease, dissatisfaction with conventional medicine, positive relationship with staff and doctors of the integrative medicine clinic providing OPT, and benefits of OPT, among others. Although many patients expressed feeling doubts towards the practice of OPT at first, many seemed satisfied with the results of the practice, mainly because they were able to manage their symptoms and gain a sense of control. This may have led to an increase in QOL. The mixed methods design was able to inform the interpretation of the association of OPT with reported increase in QOL in the quantitative phase of the research.