Although the benefit of updated therapeutic regimens, including bortezomib, on the survival of immunoglobulin light chain (AL) amyloidosis patients with heart failure (HF) has been reported, predictors of mortality in the patients treated with the updated therapy remain unclear. We retrospectively enrolled AL amyloidosis patients who had severe HF at the time of diagnosis and received the updated therapy, including bortezomib (n = 19, 61 ± 6 years old, 68% male). Severe HF was defined as the presence of both NYHA functional class III or IV and BNP > 200 pg/ml or NT-pro-BNP > 900 pg/ml. One-year mortality rate during follow-up after commencement of the treatment was 37%. Left ventricular morphological parameters and indexes of left ventricular diastolic function on admission were similar in the non-survivors and survivors. However, non-survivors had higher incidences of atrial fibrillation and ventricular tachycardia, higher serum total bilirubin levels (1.34 ± 0.55 vs. 0.61 ± 0.29 mg/dl), higher right atrial volume index (RAVI 49.7 ± 29.9 vs. 27.3 ± 6.8 ml/m²), lower tricuspid annular peak velocities during systole (RVs’ 8.0 ± 1.8 vs. 11.6 ± 3.7 cm/sec) and late diastole (RVa’ 3.4 ± 0.9 vs. 11.4 ± 5.3 cm/sec), and larger inferior vena cava dimension (22.7 ± 6.4 vs. 16.3 ± 4.9 mm) than those in survivors. Kaplan–Meier curve analyses showed that larger RAVI and lower RVs’ and RVa’, but not left ventricular systolic/diastolic dysfunction, predicted higher mortality during 1-year follow-up. The present results suggest that the presence of right-sided heart abnormality on admission is associated with high 1-year mortality in AL amyloidosis patients with severe HF under the updated therapeutic regimens.