In an interview with the local Al-Kitab television channel, Haniyeh said the decision was aimed at expediting Palestinian reconciliation.
More than 400 Fatah members and leaders left Gaza in 2007 after violence erupted between the movement, to which Palestinian Authority President Mahmoud Abbas belongs, and Hamas, which won Palestinian legislative elections in early 2006.
Hamas forces eventually routed troops loyal to Fatah and seized control of the coastal strip.
On Monday, Haniyeh said his government would forge ahead with reconciliation efforts, adding that all the measures recently adopted by his government served to confirm this.
He stressed that reconciliation must be based on consensus regarding the need to support resistance against Israel's ongoing occupation of Palestinian land.
Earlier this month, Haniyeh declared that 2014 would be "the year of Palestinian reconciliation," adding that all Fatah members who fled the strip in 2007 were welcome to return – with the exception of those charged with wrongdoing.
The prime minister also said that Gaza's Interior Ministry would release Fatah members arrested earlier on political charges, while stressing that the number of such prisoners was minimal.