This study aimed to translate three English-language instruments—Pain Knowledge and Use (PKU), Collaboration and Satisfaction About Care Decisions (CSACD), and Environmental Complexity Scale (ECS)—into Korean and evaluate the equivalence of the instrument versions. Three Korean translators and two senior reviewers translated the instruments’ 56 items using a committee approach. Eight Korean experts evaluated the cultural relevance of the translated instruments using a content validity index (CVI), and 12 Korean neonatal nurses were interviewed to assess their understanding of items. In an expert panel review, the item-CVI was less than 0.78 for 14 items. Based on cognitive interviews, four items were found to be unsuitable in Korea. Based on expert panel review and cognitive interviews, unsuitable items were modified or deleted. In another expert panel review, the scale-CVI was 1.00 for the final instruments. The findings support the validity of the Korean-language PKU, CSACD, and ECS for research application.