Background: In the United States, melanoma is the fifth most common type of cancer. Reducing UV radiation (UVR) exposure is essential for the prevention of melanoma. The assessment of individual-level UVR exposure using wearable technology is a promising method to monitor and reduce UVR exposure. However, the feasibility and acceptability of using wearable UVR monitoring devices have not been assessed. Objective: This study aimed to assess the feasibility and acceptability of using a commercially available UVR monitoring wearable device in adults and children. Methods: We recruited families (1 parent and 1 child) to test a new, commercially available UVR monitoring device (namely, Shade). Participants wore Shade for 2 weeks and completed questionnaires assessing the feasibility and acceptability of wearing the device. Qualitative analyses were conducted to summarize participants’ open-ended responses regarding device feasibility. Results: A total of 194 individuals (97 adults and 97 children) participated in this study. The participating children were aged, on average, 12.7 years. Overall, adults and children reported moderate satisfaction with wearing Shade. The feasibility of the use of Shade was adequate, with 73% (65/89) of adults and 61% (54/89) of children reporting that they wore the device “all of the time they were outside.” Through open-ended responses, participants reported that the device was easy to use, was compact, and increased their awareness about their exposure to UVR. Conclusions: Adults and children can feasibly use a wearable UVR monitoring device, and the use of the device was acceptable to participants. The device could be integrated into melanoma preventive interventions to increase individuals’ and families’ awareness of UVR exposure and to facilitate the use of recommended melanoma preventive strategies. [JMIR Dermatol 2020;3(1):e15711]