Striker MacDonald and midfielder Hardie played little part in Saints' first top-flight season for seven years after their injury-plagued spells at McDiarmid Park continued.
MacDonald has undergone two cartilage operations after being hurt scoring in February's Scottish Premier League game at Kilmarnock, while Hardie required knee reconstruction after suffering a horror injury in a behind-closed-doors game with Falkirk in November.
MacDonald, 29, told his club's official website: "I'm delighted to get a contract and I'm determined to repay the gaffer for his faith in me.
"Obviously, when you're injured and going out of contract, it's a worry but I'll be back for pre-season and it can't come soon enough for me."
Hardie, 34, added: "Everybody knows I've been out quite a long time. At least my future's sorted.
"It's now up to myself to prove to people like the gaffer upstairs that I'm going to be back fit and playing again."
Manager Derek McInnes said: "Peaso will be ready for pre-season and Martin should be back in September. They have both been good servants and shown their value in the SPL."
Source: Team Talk
Source: Team Talk