The W114/W115 models were the first post-war Mercedes-Benz production car to use a newly engineered suspension, not derived from preceding models. The new format of semi-trailing rear arms and ball-joint front end first displayed in the W114/W115 would be used in all new Mercedes passenger car models until the development of the multi-link rear suspensions of the 1980s. The W108/109 S-Class of the 280S/8, 280SE/8 and 300SEL/8 (and W113 230SL, 250SL and 280SL "Pagoda") would be the last of the low-pivot swing axle and king pin/double wishbone front ends. The next S-Class, the W116, had the same engineering as the W114/115.

The Mercedes-Benz W114/W115 was the mid-sized saloon model for Mercedes, positioned below the S-Class. Mercedes also launched its first 5-cylinder diesel engine OM617 in this chassis. It followed heavily in the direction set by the W108/109 S-class, which was launched in 1965 and heralded the new design idiom. The car was designed by French auto designer Paul Bracq who was chief designer at Mercedes-Benz for models from 1957 to 1967, a period that included models such as the Grosser Mercedes-Benz 600. Bracq was also responsible for BMW designs (1970–74) and Peugeot designs (1974–96).