However, the new policy, which arrives at the conclusion of a seven-month review, would allow even troops in the field access to those Web sites on the Pentagon's non-classified network.
Those sites have been banned since 2007, according to the Pentagon.
However, commanders will still have the ability to cut access to Facebook, Twitter and other networks to safeguard their missions or local networks. But the Pentagon specified last week leaders could only block such content on temporary basis; access must eventually be restored.
"This directive recognizes the importance of balancing appropriate security measures while maximizing the capabilities afforded by 21st Century Internet tools," Deputy Secretary of Defense William J. Lynn III said Friday in a statement.
Facebook later heralded the decision, noting the Pentagon had already set up its own page that has attracted thousands of fans.
“Facebook is heartened by today’s decision to begin to allow our nation’s men and women in uniform and civilian employees across the Department of Defense responsible access to social media, which plays an important role in people’s daily lives," said Don Faul, director of Online Operations at the popular network.
"Facebook is an efficient way for people with real-world connections to share information and communicate and can be a particularly beneficial link between those stationed around the world and their families at home,” he said.