Purpose: Serum albumin can indicate the onset of cancer cachexia, provide information about a patient's nutritional status, and serve as a biomarker for the prognosis of patients with cancer cachexia. However, the relationship between serum albumin levels and mortality in patients with cancer cachexia remains unclear. We aimed to examine the association of albumin and total protein with 1-year mortality in patients with cancer cachexia. Patients and Methods: We conducted a nested case-control study using data from a multicenter cancer clinical survey from 2013 to 2018. In total, 266 patients with cancer cachexia who survived for <1 year and 266 patients who survived for >= 1 year were included in this study. The participants were matched by age, sex, tumor type, tumor stage, and hospital site. The crude and adjusted risks of 1-year survival were estimated using odds ratios (ORs) and 95% confidence intervals (95% CIs) using logistic regression, with or without adjustment for covariates. Results: Logistic regression analysis revealed a significantly negative linear association between albumin level and 1-year mortality in patients with cancer cachexia (p < 0.001). An L-shaped relationship existed between total protein and 1-year mortality, with a turning point at 70.4 g/L. When albumin was divided into quartiles, Q3 (OR: 0.40; 95% CI: 0.24, 0.68; p < 0.001) and Q4 (OR: 0.33; 95% CI: 0.19, 0.55; p < 0.001) were associated with higher 1-year survival than Q1 among patients with cancer cachexia. When total protein was divided into quartiles, Q2 (OR: 0.38; 95% CI: 0.23, 0.64; p < 0.001), Q3 (OR: 0.57; 95% CI: 0.33, 0.96; p = 0.035), and Q4 (OR: 0.43; 95% CI: 0.25, 0.72; p = 0.002) were associated with higher 1-year survival than Q1 among patients with cancer cachexia. Conclusion: Serum albumin and total protein may predict 1-year survival. Future clinical studies should lead to a more comprehensive understanding of the effects of serum protein levels in patients with cancer cachexia.