Increasing need of nursing care has led to increased burden on formal caregivers, where those in nursing homes have to deal with exhausting labor. Although research activities on the use of IoT devices to support nursing care for older adults exist, there is limited evidence on the effectiveness of these interventions among formal caregivers. We aim to investigate whether mat type sleep state sensors for supporting nursing care can reduce mental burden of formal caregivers in a nursing home. An intervention group received sleep state sensors to provide nursing care for residents in all private rooms on the 4th floor of the nursing home. The sleep state sensors were mat types and designed to detect body motion such as the frequency of toss-turning and to measure heartbeat and respiration. One sensor was placed on a bed in a private room. When body motion is detected, the information is instantly displayed on a monitor at a staff station. In addition, the mental condition of the participants was measured using the Profile of Mood States (POMS). Participants in both groups received the POMS at baseline, midpoint, and endpoint to identify changes in these domains. The primary outcome was the difference in total mood disturbance (TMD) of the POMS at baseline and week 8. Of 22 eligible formal caregivers, 12 formal caregivers utilized sleep state sensors for eight weeks. The remaining 10 formal caregivers provided nursing care as usual. As for the primary outcome of the difference between TMD at baseline and week 8, TMD in the intervention group improved by -3.67 versus 4.70 in the control group, resulting in a mean difference of -8.37 (95% CI -32.02–15.29; p = 0.48). In conclusion, the present 8-week study showed sleep state sensing for elderly residents might not be associated with reduced mental burdens on formal caregivers in nursing homes.