Williams has confirmed that Smedley "will strengthen the trackside team whilst also supporting the development work back at the factory".
While Massa has also joined the team from Ferrari, he will not be race engineered by the Briton.
AUTOSPORT understands that the need to ensure the factory is best serving the race team has been targeted as an area of improvement for Williams since chief technical officer Pat Symonds took over last year.
Smedley will be key to this process, effectively assuming a senior role in the garage that will ensure the link between track and base works as effectively as possible.
Williams has also confirmed that Richard Lockwood has joined from Marussia, where he worked as a tyre/strategy engineer. He has been appointed head of race strategy to work with incumbent strategist Randeep Singh.
These are the latest in a series of moves to push the team back up the grid following the recruitment of Rod Nelson to run the testing operation and Jakob Andreasen as head of engineering operations.
"Williams is undergoing change and these new appointments reflect how high our ambitions are," said Symonds.
"We have a number of senior people joining us to assist us in the pursuit of those ambitions and I am extremely excited to welcome them on-board.
"2014 gives us the biggest change to the technical regulations that I have seen in my career, and so it will be important to add further depth to the talent we already have here as we head into the new season.
"Williams has always prided itself on engineering excellence and this latest announcement is part of our continued goal to bring success back to the team."
The team has also confirmed that Pastor Maldonado's 2013 race engineer, Andrew Murdoch, will work with Massa with Jonathan Eddolls continuing with Valtteri Bottas.
Xevi Pujolar, chief race engineer at Williams last year, has moved to Toro Rosso where he will work with Jean-Eric Vergne.