Thermal care is a critical part of caring for neonates. The need to identify simple, affordable and effective tools for detecting hypothermia in newborn infants that can be used by mothers and other caregivers in resource-poor countries remains crucial in our efforts to reduce perinatal and neonatal mortality and morbidity. The objective of this study was to determine the effectiveness of ThermoSpot in detecting hypothermia in newborn infants in a developing country. The prevalence of hypothermia (< 36 degrees C) in our study population was 51.4%. The ThermoSpot disc indicated green (normothermia) in 82% of infants whose axillary temperature was between 32 and 35.9 degrees C. However, the disc had a 100% specificity and positive predictive value at body temperatures below 36 degrees C and axillary temperatures below 36 degrees C or above 37.5 degrees C. Sensitivity, negative predictive value and accuracy were 19%, 52% and 57%, respectively. Mortality was significant in infants with black or blue ThermoSpot disc colours compared with green. For ThermoSpot discs placed on the abdomen, the risk of dying was 2.67 times higher if the disc colour was black compared with green and 2.43 times higher if the disc colour was blue compared with green. Similarly for ThermoSpot discs placed in the axilla, the risk of dying was 2.54 times higher if the disc colour was black and 2.5 times higher if the disc colour was blue as opposed to green. There is a need to improve the sensitivity and accuracy of ThermoSpot in detecting hypothermia before its widespread use.