The 18-year-old, who will stay at the Coral Windows Stadium until January 2015, will be in contention for Saturday's league game at Walsall but did not register in time for Tuesday's Capital One Cup tie at Morecambe.
Parkinson told the club's official website: "We are delighted by Mason's arrival.
"I'm sure he will be a great addition to the squad and we look forward to working with him over the coming months."
Bennett, a product of Derby's academy who can also operate out wide, became the club's youngest-ever player when he made his debut aged 15 in 2011. He has made 32 appearances for the Rams.
He signed a new four-year deal with Derby at the end of last month following a spell on loan last season at Chesterfield and has represented England at U-16, U-17 and U-19 level.