Held for the first time, the BusinessCar Awards reward manufactures and companies involved in fleet management, leasing and business vehicles.
The C-Class was given the 'Best Premium Car' award while the 'Best Luxury Car' award was given to the S-Class.
Debbie Wood, BusinessCar's editor, said: "In terms of comfort, tech and efficiencies, the Mercedes-Benz C-Class sets a very high bar in the premium car sector and its strong residual value means it makes a great deal of sense on paper too."
"Meanwhile, the S-Class, fresh from a midlife facelift ,remains the sector's car of choice. It;s well connected in ever sense , and supremely comfortable and safe too. Both cars proved hugely popular with our judges this year, and when it comes to luxury, Mercedes-Benz continues to be the manufacturer to beat. "