Background: Serum C-reactive protein (CRP) levels are correlated with patient outcomes in cancer. This study aimed to determine associations between the CRP level and the dietary intake, symptoms, and eating-related distress (ERD). Methods: We conducted a multicenter survey among advanced cancer patients. Information on patient characteristics was retrieved from the electronic medical records. Data on patient outcomes were obtained through the questionnaire. Patients were categorized into the low CRP group (<5 mg/dL) and the high CRP group (≥5 mg/dL). Comparisons were calculated using the Mann–Whitney U test or chi-squared test. To assess associations between CRP levels and ERD, multivariate logistic regression analysis was performed. Results: A total of 191 patients were enrolled and divided into the low CRP group (n = 117) and the high CRP group (n = 74). The high CRP group had a more reduced dietary intake (p = 0.002) and more severe appetite loss (p = 0.008). The total scores of the ERD questionnaire (both the long and short versions) were significantly higher in the high CRP group (p = 0.040 and 0.029). The high CRP group also had significantly higher risks for ERD, as assessed using the long and short versions of the questionnaire (odds ratio [OR] 2.13, 95% confidence interval [CI] 1.10–4.11; OR 2.06, 95% CI 1.05–4.05). Conclusions: High CRP levels were significantly associated with reduced dietary intake, appetite loss, and ERD. A serum CRP value of 5 mg/dL may be a useful indicator for initiating cancer cachexia care.