The objectives of this descriptive research were: to investigate the clinical judgment of nurses regarding postoperative pain, their caring behaviors in postoperative pain management, and the relationship between nurses’ clinical judgment regarding postoperative pain and nurses’ caring behaviors in postoperative pain management. A sample of 260 professional nurses who worked in the surgical wards of two regional and two provincial hospitals in southern Thailand under the Ministry of Public Health administration were used in the study. The content of the instruments were all validated. The internal consistency reliability coefficients of the two parts of nurses’ caring behavior in the postoperative pain management questionnaire were 0.72 and 0.78 and for nurses’ clinical judgment regarding postoperative pain questionnaire was 0.85. The data were analysed using descriptive statistics and Spearman’s Rank Correlation. The results indicated that subjects rated nurses’ clinical judgment regarding postoperative pain as ‘good’ with a mean of 3.98 (score 1-5). It was also found that the aspect in which nurses made the best clinical judgment was in understanding of the patients with a mean of 4.19. Overall, the subjects rated nurses’ caring behavior in postoperative pain management as ‘good’ with a mean of 34.26. (total score = 37). There was no significant relationship between nurses’ clinical judgment regarding postoperative pain and nurses’ caring behaviors in postoperative pain management. This finding may be partly due to the restricted range of scores on these two questionnaires. A replication study is recommended and further development of the instruments, particularly nurses’ clinical judgment questionnaire is suggested.