Raha was handed over the baton of the COSC by Gen Singh at a ceremony in South Block, Defence officials said. Raha, 59, will hold the office for a period of 29 months and would probably be the longest-serving officer in the chair.
He has got the long tenure because of the resignation of former Navy Chief Admiral DK Joshi in February after a series of mishaps involving naval warships.
Raha will continue in office till December 2016 and is expected to push for increasing jointmanship among the three services as the CoSC.
He is also expected to push for the creation of three new tri-services commands including Space, Cyber and Special Operations.
The proposal for raising the three new formations is with the government for quite some time now and deliberations are being held between all the stakeholders for an early decision on the issue.