Pradeep Singh was arrested from Baramulla. Police say he provided shelter to two of the four militants who had targeted the Central Reserve Police Force (CRPF) camp in Bemina on Wednesday.
Pradeep Singh's arrest is the third in the case. Two suspected Pakistani militants have been arrested from Chhattabal in Srinagar.
Police said Bashir, a surrendered militant who was arrested on Thursday night, led to Zubeer alias Talha Zarar, a resident of Multan in Pakistan. While the state police believe Zubeer entered India along with five others in February, central intelligence agencies say he crossed over into India alone in January.
Five CRPF jawans were killed and 12 people, including eight jawans, were injured when militants, carrying what looked like cricket bags, entered the CRPF camp and opened fire. The attack was the first in Srinagar in three years.
Home Minister Sushil Kumar Shinde said in Parliament that the militants appeared to be Pakistanis.