The prognosis of advanced lung adenocarcinoma (LUAD) remains unfavorable, with chemotherapy constituting a primary treatment modality. Discerning the efficacy of chemotherapy for advanced LUAD is imperative. Prior investigations have demonstrated the prognostic value of albumin and D-dimer individually for malignancies; however, the predictive capacity of albumin-to-D-dimer ratios (ADR) for advanced LUAD subjected to first-line platinum-based chemotherapy remains unexplored. A cohort of 313 patients with advanced LUAD was retrospectively examined in this study, spanning from January 2017 to January 2021. ADR threshold values were ascertained via receiver operating characteristic analysis, followed by the evaluation of the association between pretreatment ADR and clinicopathological characteristics, disease control rate (DCR), and overall response rate (ORR) pertinent to first-line chemotherapy. Prognostic factors for progression-free survival (PFS) were determined employing Cox univariate and multivariate analyses. Subsequently, survival data were illustrated utilizing the Kaplan-Meier method and scrutinized through the log-rank test across the entire and subgroup populations. ADR demonstrated a superior area under the curve (AUC) value relative to albumin and D-dimer individually and exhibited enhanced prognostic predictive capability compared to albumin-to-fibrinogen ratios (AFR) for advanced LUAD (AUC: 0.805 vs. 0.640, DeLong test: p<0.001). ADR yielded a cut-off value of 16.608. A greater proportion of non-smokers was observed within the high-ADR group (ADR>16.608) compared to the low-ADR group (ADR≤16.608). Patients in the high-ADR group displayed elevated BMI and Na+ levels and reduced neutrophil count, monocyte count, globulin, and alkaline phosphatase (all p<0.05). Notably, the high-ADR group exhibited heightened DCR (96.7% vs. 89.2%, p=0.008) and ORR rates (70.1% vs. 51.0%, p=0.001) relative to the low-ADR group. Multivariate analysis outcomes indicated that high ADR constituted an independent risk factor for PFS (hazard ratio: 0.24, p<0.001). Furthermore, patients in the high-ADR cohort displayed a significantly prolonged median PFS (254 vs. 142 days, p<0.0001) compared to their low-ADR counterparts. In subpopulations exhibiting favorable implications for PFS, as determined by multivariate analysis, high-ADR patients consistently demonstrated extended PFS durations relative to the low-ADR group (all p<0.0001). Collectively, our findings suggest that ADR constitutes a novel and promising prognostic indicator for advanced LUAD patients, surpassing the accuracy of albumin and D-dimer individually and AFR. ADR thus serves as a potent instrument for assessing treatment effects and PFS in advanced LUAD patients undergoing first-line chemotherapy.