The Nociception Coma Scale (NCS) is a pain observation tool, developed for patients with disorders of consciousness (DOC) due to acquired brain injury (ABI). The aim of this study was to assess the interrater reliability of the NCS and NCS-R among nurses for the assessment of pain in ABI patients with DOC. A secondary aim was further validation of both scales by assessing its discriminating abilities for the presence or absence of pain. Hospitalized patients with ABI (n = 10) were recorded on film during three conditions: baseline, after tactile stimulation, and after noxious stimulation. All stimulations were part of daily treatment for these patients. The 30 recordings were assessed with the NCS and NCS-R by 27 nurses from three university hospitals in the Netherlands. Each nurse viewed 9 to 12 recordings, totaling 270 assessments. Interrater reliability of the NCS/NCS-R items and total scores were estimated by intraclass correlations (ICC), which showed excellent and equal average measures reliability for the NCS and NCR-R total scores (ICC 0.95), and item scores (range 0.87-0.95). Secondary analysis was performed to assess differences in ICCs among nurses' education and experience and to assess the scales discriminating properties for the presence of pain. The NCS and NCS-R are valid and reproducible scales that can be used by nurses with an associate (of science) in nursing degree or baccalaureate (of science) in nursing degree. It seems that more experience with ABI patients is not a predictor for good agreement in the assessment of the NCS(-R).