Background: Intracardiac thrombus is a clinically important complication of acute myocardial infarction (AMI), particularly in patients with ventricular aneurysm. We examined the contemporaneous associations of anterior ventricular involvement and D-dimer with echocardiographically documented intracardiac thrombus with incomplete chamber-specific localization among hospitalized AMI patients with ventricular aneurysm. Methods: This retrospective analysis included 1684 patients with documented ventricular aneurysm from a final cohort of 17,950 hospitalized AMI patients treated between January 2018 and October 2025. The first D-dimer measurement obtained at our hospital after AMI confirmation was used for D-dimer analyses. Ventricular aneurysm and intracardiac thrombus status were determined from the available echocardiographic documentation during the index hospitalization. Aneurysm locations were coded as linked patient-level, non-mutually exclusive indicators. Logistic regression evaluated anterior involvement; missing model covariates were multiply imputed and regression estimates were pooled using Rubin’s rules. Collinearity diagnostics and sensitivity analyses restricted to patients with apical aneurysm, including a complete-case analysis, were performed. Model-performance measures were interpreted as exploratory apparent performance in the development dataset. Results: Intracardiac thrombus was documented in 211 of 1684 patients (12.5%). Anterior involvement was more frequent among patients with thrombus than among those without thrombus (57.3% vs. 45.0%; p < 0.001) and remained associated with thrombus in the primary anatomical and clinical model (OR, 1.63; 95% CI, 1.20–2.21; p = 0.002). D-dimer was available in 1633 patients. On the log2-transformed scale, each doubling of D-dimer was associated with higher odds of echocardiographically documented intracardiac thrombus (adjusted OR, 1.24; 95% CI, 1.14–1.34; p < 0.001). As a complementary descriptive analysis, the observed thrombus proportion increased from 3.63% in Q1 to 22.30% in Q4; compared with Q1, the adjusted ORs were 3.71, 5.22, and 9.50 in Q2, Q3, and Q4, respectively. The combined model had a mean apparent AUC of 0.716, compared with 0.713 for the model containing D-dimer without anterior involvement; the mean absolute increment was approximately 0.003. Conclusions: Among hospitalized patients with AMI and ventricular aneurysm, higher D-dimer levels and anterior ventricular involvement were associated with echocardiographically documented intracardiac thrombus. Chamber-specific localization was incomplete, and these contemporaneous associations do not establish causality or prospective prediction. Anterior involvement provided minimal incremental discrimination beyond D-dimer.