Ellis is currently Red Bull's head of vehicle dynamics and Wood chief engineer for simulation.
"These two newly-created roles will further strengthen the team's technical organisation, particularly in the fields of simulation and vehicle dynamics," Mercedes added.
The two men are the first major signings by the team since the departure of principal Ross Brawn was announced, with executive directors Paddy Lowe and Toto Wolff sharing the leadership tasks.
Red Bull, with Sebastian Vettel, have been champions for the past four years and were dominant in the second half of the 2013 season with their 26-year-old German driver winning the last nine races in a row.
However they have suffered some important staff losses, with McLaren trumpeting the signing of aerodynamicist Peter Prodromou for 2015, when the Woking-based team will have Honda as engine partners.
(Reporting by Alan Baldwin, editing by Sudipto Ganguly)
