A 2-week, randomized, double blind, and controlled study was designed to evaluate the therapeutic effectiveness and safety of a neurofeedback wearable device for stress reduction. Participants were healthy adults with psychological stress and subclinical symptoms of depression or anxiety. Subjects practiced either neurofeedback-assisted meditation (n = 20) or neurofeedback non-assisted meditation (n = 18) for 12 minutes twice a day for a total of two weeks. Outcome variables were questionnaires of stress, mood, and sleep, quantitative electroencephalogram (qEEG), and blood tests. Regarding the Perceived Stress Scale, the experimental group had a significantly decreased score compared to the control group (6.45 ± 0.95 vs. 3.00 ± 5.54, p = 0.037). State anxiety tended to have a greater effect in the experimental group than in the control group (p = 0.078). Depressive mood and sleep were also improved in each group, showing no difference between the two groups. There were no significant differences in stress-related physiological parameters such as stress hormone or qEEG between the two groups. In the satisfaction evaluation of device use measured at final visits, subjective device satisfaction was significantly higher in the experimental group than in the control group (p = 0.008). Thus, neurofeedback-assisted meditation using a wearable device can help improve subjective stress reduction compared to non-assisted meditation. These results support neurofeedback as an effective adjunct to meditation to relieve stress.