The developments regarding the dependable full-back, 24, follows on from the recent news that midfielder Jonathan Hogg had also agreed fresh terms with the club, signing a three-year deal.
Smith’s existing contract was due to run until 2018, with this new deal running for a further year.
On the new deal for Smith, who linked up with Town ahead of the 2012-13 season, head coach David Wagner said: “I am very happy that Tommy has extended his stay at Huddersfield Town for even longer, as he is an important player for this club.
“He has worked very hard to improve his game since I arrived at the club back in November and he still has further room for development. That is exciting for everyone, as I already believe he is a top right back for this division.
“Tommy’s character is excellent and I know he will keep working hard on the training pitch to get better and better.
“Signing up Tommy reaffirms our commitment to keeping the best players at the club, following on from Jonathan Hogg, Philip Billing, Joe Lolley and Harry Bunn all signing new contracts too. This has always been big for us.”