This study aimed to investigate long-term effects of the flotation–REST (restricted environmental stimulation technique) 4 months after treatment. Seventy patients, 54 women and 16 men, participated, diagnosed as having stress-related pain. Twenty-six participants had also the diagnosis of burnout depression. Participants were randomly assigned in equal numbers to either a control group or a flotation–REST group and participated in a total of 12 flotation–REST or control sessions. Results indicated that pain areas, stress, anxiety, and depression decreased, whereas sleep quality, optimism, and prolactin increased. Positive effects generally maintained 4 months after treatment, but prolactin returned to initial levels. It was concluded that flotation tank therapy is an effective method for the treatment of stress-related pain.