Thirty-year-old Macleod has put pen to paper on a two-year extension, while youngster Harrison has agreed a new three-year contract with the club.
Director of rugby Steve Diamond told the club's official website: "As far as Nick is concerned, he's a model professional who has been at the club for five years now and he's a great player at number 10.
"He's a really popular guy with all of the squad and he's does a good job whenever he plays. As regards Ross, he comes out of the Henry Thomas, Tommy Taylor and James Gaskell camp.
"He's definitely got a full representative future with England ahead of him if he carries on in the way he's going."
Diamond has also claimed that he expects a number of contract renewals within the squad to be done over the next few weeks.