The 23-year-old former Chelsea Academy graduate has impressed in his seven appearances for the Royals this season.
And manager Brian McDermott and chairman Sir John Madejski have been suitably impressed to offer 2009 signing Cummings a fresh two-and-a-half-year deal.
"I'm very excited to remain at a club that has such ambition in the Premier League," Cummings told Reading's official website.
"To have already played against the likes of Manchester United and Liverpool is great experience at my age so I can't ask for anything more.
"Everyone wants to fight for their shirt and play in the Premier League - and everyone knows what we've got to achieve to stay here."