Del Zotto began his hockey career with the Stouffville Clippers A of the Whitchurch-Stouffville Minor Hockey Association (WSMHA). He then played for the Richmond Hill Stars and the Markham Waxers in the OMHA’s Eastern AAA League (OMHA).
In his second season with Oshawa, Del Zotto’s 63 points ranked him third among defencemen in the OHL. He made his second OHL playoff appearance when the Oshawa Generals got to the third round in the 2008 OHL playoffs. Del Zotto was chosen for the 2008 CHL Top Prospects Game.
On January 8, 2009, Del Zotto was part of a trade that would send him, along with teammates John Tavares and Daryl Borden, to the London Knights for prospects Christian Thomas, Scott Valentine, Michael Zador and six draft picks.
On October 2, 2009, Del Zotto made his NHL debut against the Pittsburgh Penguins. At age 19, he became the youngest defenceman in Rangers history to play on an opening night. Del Zotto scored his first NHL goal the next day, against Pascal Leclaire of the Ottawa Senators, in the Rangers’ home opener. Del Zotto proved he was an asset to the team and, as a result, averaged 20–25 minutes per game.
Del Zotto was awarded the NHL’s Rookie of The Month for October 2009 after posting 12 points in his first 14 professional games. After his first year in the league, Del Zotto was named to the 2010 NHL All-Rookie Team.
On January 31, 2011, the New York Rangers recalled Del Zotto from the Connecticut Whale back to the NHL.