The former England under 19 international, who was the Gulls' captain in the National League last season, signed a two-year deal with Barnsley this week after the Reds paid an undisclosed fee. He will hope to break up a centre-back combination which was one of the tightest in the Football League as Barnsley gained promotion last season.
"I am really happy to be at Barnsley," MacDonald, 23, told the Chronicle.
"Going up three divisions is a big leap but I've always wanted to get back into the Football League so I am delighted. I've come here to play so I will be looking to compete with Alfie and Marc for a place in the team. "They are really good players who I can learn off."
MacDonald is suspended for tomorrow's trip to Ipswich as he picked up 15 bookings last season.
He said: "It's not ideal but hopefully I can be involved against Northampton on Tuesday. I just want to adapt to the new area and to the system we play quickly. The team is obviously on a great run after going from bottom of League One to getting promoted. The first aim is to stay up but after that we want to finish as high as possible."
