The purpose of this study was to examine the reliability and validity of the Turkish version of the Nursing Activities Score. To validate the Turkish version of the Nursing Activities Score, a sample comprising 30 adult intensive care patients and 30 nurses was employed. After a pilot study, the internal consistency, Cronbach's alpha coefficient, was found to be p = 0.718. Following the significant internal consistency obtained in the pilot study, the correlation between Nursing Activities Score internal consistency and Critical Nursing Situation Index scores was examined in 150 adult intensive care patients and 150 nurses. The assessment of inter-rater reliability showed a high level of agreement (99%) and an average Kappa index of 0.598 (p < 0.001). Concurrent validity was demonstrated through a statistically significant correlation between Nursing Activities Score and the Critical Nursing Situation Index (r = 0.71, p < 0.001) and multivariate regression analysis (R2 = 83%, p < 0.001). The validity is supported by the statistically significant relationship between Nursing Activities Score and Critical Nursing Situation Index. These results demonstrate that Nursing Activities Score is a valid and reliable tool for measuring nursing workload in Turkish intensive care units. Samsun University Samsun Training and Research Hospital, following ethics committee approval (Samsun University clinical research ethics committee (KAEK) 202312/2) and Clinical Trials (NCT04928040) registration.