We present here a case of severe congestive cardiac failure, in a 47-year-old patient with myeloma who had no prior cardiac history, after receiving bortezomib. Bortezomib is a boron-containing molecule, which reversibly inhibits the proteasome, an intracellular organelle, which is central to the breakdown of ubiquitinated proteins and consequently crucial for normal cellular homeostasis. Phase II clinical trials demonstrate that it is effective for the treatment of relapsed refractory myeloma. Acute development of congestive cardiac failure associated with bortezomib therapy occurs very rarely or may be underestimated. Inhibition of proteasome activity may impair cardiac function due to accumulation of unfolded, damaged and undegraded proteins in myocytes. Patients with or without cardiac disease or previously received anthracycline-containing regimes should be closely monitored when being subjected to treatment with bortezomib.