PURPOSE: This study aimed to determine factors associated with multimodal care practices for cancer cachexia among registered dietitians (RDs) working in cancer care. METHODS: A secondary analysis was performed using RDs' data. Data on knowledge, skills, and confidence in multimodal care were obtained. Nine items regarding multimodal care practices were evaluated. Subjects were divided into two groups based on their answers associated with the nine items. Comparisons were obtained using the Mann-Whitney U test or chi-squared test. Multiple regression analysis was performed to identify the critical factors involved in practicing multimodal care by determining the variables with significant differences between the two groups. RESULTS: Two hundred thirty-two RDs were included in this study. Significant differences were observed in their primary area of practice (p = 0.023), the number of clinical guidelines used (p < 0.001), the number of items used in cancer cachexia assessment (p = 0.002), the number of symptoms used in cancer cachexia assessment (p = 0.039), training for cancer cachexia (p < 0.001), knowledge of cancer cachexia (p < 0.001), and confidence in cancer cachexia management (p < 0.001). The number of symptoms used in cancer cachexia assessment (B = 0.42, p = 0.019), knowledge of cancer cachexia (B = 6.60, p < 0.001), and confidence in cancer cachexia management (B = 4.31, p = 0.010) were identified as critical factors according to the multiple regression analysis. CONCLUSION: The RDs' knowledge and confidence in cancer cachexia management were associated with their multimodal care practices.