The 21-year-old academy product has made 26 appearances for the Giants since his Super League debut in 2018.
Huddersfield head coach Ian Watson said: "Innes has grown from strength to strength in his time as a Giants player and has grown his confidence and his ability in his time at the club and has been rewarded with a new contract.
"It's great to see so many young players who have progressed through the Giants system staying with the club and helping us build.
"He has been exceptional this season and we're looking forward to seeing how he progresses over the next two years."
Senior has also gained experience during loan spells with Workington Town and Wakefield Trinity.
"I'm delighted to sign a new deal to keep me at Huddersfield Giants," said the outside back.
"I want to continue developing and improving my game at the Giants and I hope to continue on the path I've started since I made my debut here.
"It's great to continue my career at my hometown club and I'm looking forward to continuing to compete for a starting spot."