The global policy, which will begin on 1 January 2016, is part of Facebook’s aspiration to become one of the top businesses for families.
The news comes after CEO Mark Zuckerberg recently announced he will be taking two months off after the birth off his first child.
Lori Goler, vice president of human resources and recruiting, said in the update: "I am proud to announce that we are extending our parental leave policy for full time employees to cover four months of paid baby leave for all new parents, no matter their gender or where in the world they live."
Facebook CEO Mark Zuckerberg is taking two months off after the birth of his first child
Goler continued: "This expanded benefit primarily affects new fathers and people in same-sex relationships outside the US. It will not alter the existing maternity leave currently available to all employees worldwide.
"All new parents in all of our offices worldwide, including those who had or adopted a baby in 2015 and were Facebook employees at the time, will be eligible.
"Our approach to benefits at Facebook is to support our employees and the people who matter most to them. We want to be there for our people at all stages of life, and in particular we strive to be a leading place to work for families."
Goler said the company decided to make the change because studies show when working parents take time to be with their newborns, outcomes are better for the children and families.
The leave can be taken at any point up to a year after the baby is born.
She added: "For too long, paid baby leave has been granted only to a mother who is giving birth.
"We believe that fathers and mothers alike deserve the same level of support when they are starting and growing a family, regardless of how they define family."
Earlier in November 2015, Zuckerberg, who revealed he was expecting his first child with wife Priscilla Chan in August 2015, announced much paternity leave he would be taking.
He wrote in the post on Facebook: "This is a very personal decision, and I've decided to take two months of paternity leave when our daughter arrives.
"Every day things are getting a little more real for us, and we're excited to start this next stage in our lives."
The 31-year-old uploaded a photo of his pregnant wife on Thanksgiving.
"Reflecting on family, I want to share this photo Annie Leibovitz captured with my parents and sister last month. I'm looking forward to many more moments with family to come," he wrote.