Background: AL amyloidosis is a rare disorder characterized by organ infiltration of unstable misfolded light chain proteins. Diagnosis requires a high degree of suspicion, and cardiac involvement has poor outcomes. Anthracycline-based regimens are preferred for treating abdominal leiomyosarcoma (LMS) but pose a challenge in the presence of cardiac AL amyloidosis. Case: A 66-year-old male presented with bilateral leg edema and underwent evaluation for new heart failure. Echocardiography revealed preserved left ventricle ejection fraction (LVEF) with mild hypertrophy, increased interventricular septum thickness, and diastolic dysfunction. Due to concern for cardiac amyloidosis, the patient underwent nuclear scintigraphy scan, which was negative. Ongoing clinical suspicion prompted endomyocardial biopsy, which was positive for Congo Red staining, and serum studies revealed monoclonal lambda spike with increased free light chains. PET-CT was done to assess the lung nodule, revealing abdominal LMS. While Anthracycline is the drug of choice for LMS, its potential cardio-toxic effect in the presence of heart failure need be addressed. Treatment decisions involved a multidisciplinary team, resulting in bortezomib for AL amyloidosis, gemcitabine/paclitaxel for LMS, and symptomatic heart failure management. Decision-making: Anthracycline therapy was avoided due to potential cardiotoxicity. Daratumumab was added to expedite light chain reduction and minimize cardiotoxic effects. Individualized treatment considered the patient's clinical presentation and comorbidities. Conclusion: Diagnosing cardiac amyloidosis requires a high index of suspicion. Concurrent AL amyloidosis and LMS is extremely rare and presents a therapeutic dilemma, necessitating personalized management. Further research is needed to assess the potential cardio-toxic effect of anthracycline in the presence of cardiac AL amyloidosis.