"It's a four-year deal and David is thrilled to be in camp on time," agent Jim Ivler said.
Harris finished his college career with 196 tackles, four sacks, one interception, three forced fumbles and one fumble recovery. He was also a semifinalist for the Butkus Award, given to the nation's top linebacker.
"I've really liked his inherent leadership, his presence and I thought he was very fluid in the passing game in seven-on-sevens and things like that," coach Eric Mangini said of Harris during rookie minicamp. "The person we researched is the person who's here."
New York has signed three of its four draft picks - Harris, offensive lineman Jacob Bender and wide receiver Chansi Stuckey - with first-rounder Darrelle Revis, a cornerback from Pittsburgh, the only one unsigned.