Immediately after getting his M.A. degree, Hemchandra Raychaudhuri joined Bangabashi College, Calcutta, as Lecturer of History and taught there from 1913 to '14. In 1914 he joined the Bengal Education Service and taught History at Presidency College for three years from 1914 to'16. In 1916 he was transferred to the Government College, Chittagong in East Bengal and it was around this time he faced great personal distress and tragedy due to the protracted illness of his first wife and her subsequent untimely death. However, his fate soon took a turn for the better. The legendary, Sir Ashutosh Mookherjee, the first Indian Vice-chancellor of Calcutta University, who was adept at spotting extraordinary talent, approached Hemchandra with an offer of a lectureship in the newly created course Ancient Indian History and Culture. Hemchandra readily accepted, resigned from the Bengal Education Service and joined Calcutta University as a lecturer in Ancient Indian History in 1917.
So began a lifelong love affair with Ancient Indian History for Hemchandra. A passion that so consumed him that he would research, read and lecture for up to 18 hours a day! On the one hand, he expanded the frontiers of knowledge in Ancient Indian History right up to the 9th. Century B.C, by reconstructing history beyond the time of Alexander – that was the accepted documented period of Ancient Indian Historians of the time like the acknowledged authority Vincent Smith – and finding documentary evidence through his study of ancient Indian texts. On the other hand, his lectures on Ancient Indian History, became renowned for bringing alive Ancient Indian History to such an extent that generations of students swore by them, and even students of Medieval History would bunk their classes to attend them! His devoted students included names like Hem Chandra Ray, Nanigopal Mazumdar, Prabodh Chandra Bagchi, Tarak Chandra Das, Nihar Ranjan Ray, Dinesh Chandra Sircar, Sudhakar Chatterjee, Nisith Ranjan Ray, Kali Kinkar Dutta etc., who themselves later became luminaries in Indological studies.