PURPOSE Approximately 40% of childhood cancer survivors experience chronic pain, with many also reporting pain-related disability. Given associations established in the general population among respiration, anxiety, and pain, continuous tracking and feedback of respiration may help survivors manage pain. METHODS A feasibility, nonblinded, randomized controlled trial (RCT) comparing wearable respiratory monitoring with a control group examined feasibility, acceptability, and preliminary efficacy among survivors of childhood cancer with chronic pain who were = 18 years of age, able to speak and read English, lived in the United States, and had access to a smartphone and the Internet. The primary outcomes were pain interference, pain severity, anxiety, negative affect, and perceived stress. The intervention group (n = 32) received a wearable respiratory monitor, used the device, and completed an in-application breathing exercise daily for 30 days. The control group (n = 33) received psychoeducation after completion of the study. RESULTS Almost all participants in the intervention group (n = 31 of 32) and control group (n = 32 of 33) completed the study. Of those who completed the intervention, 90.3% wore the device for = 50% of the trial. Posttreatment improvement for negative affect (Cohen d = 0.59; 95% CI, 0.09 to 1.10) was significantly greater in the intervention group compared with the control group. A follow-up study (n = 24) examined acceptability and feasibility of a second-generation device among those who completed the RCT. Most survivors (81.0%) wore the device daily during the trial and 85.7% reported satisfaction with the device and the application. CONCLUSION The results of this pilot study support the acceptability and feasibility of wearable respiratory monitoring among survivors of childhood cancer. Larger randomized trials are needed to assess efficacy and maintenance of this intervention for chronic pain.