Dey, 94, who was admitted to Narayana Hrudayalaya five months ago for respiratory problems, died of cardiac arrest at 3:50 AM, a senior doctor at the hospital said.
His daughter Shumita Deb and his son-in-law Jnanranjan Deb were by his bedside when the end came, his family said.
Dey is survived by two daughters, one of whom is based in the US.
"We are saddened by his loss, but he died peacefully. His last rites will be performed later in the day," his son-in-law said.