The aid agencies, including CAFOD, have said that the conference must mobilise funds for long-term development for Syrian refugees.
In a joint report, the aid agencies argue that the conference must offer a new deal of investment for Syria's neighbouring governments that would allow Syrian refugees to better support themselves and their families financially.
Alan Thomlinson, CAFOD's Programme Manager for Syria, said: "With no end to the conflict in sight, despite a fragile peace process, and no prospect of safe return home for Syrian refugees; the Brussels Conference must deliver a new deal by providing more investment to neighbouring countries hosting refugees, in support of employment opportunities and to stimulate economic growth, that benefit both refugees and host communities alike."
The report highlights that the livelihoods and social cohesion of refugees remain underfunded.
The aid agencies argue that Syria's neighbouring governments should develop policies that allow refugees to better support themselves financially without the risk of arrest by authorities.
Since the civil war began six years ago, Turkey has taken in the most Syrian refugees, nearly 3 million, while Lebanon hosts more than 1 million and Jordan more than 600,000.
Thomlinson added: "The Brussels Conference needs to provide some benefits to host communities, and particularly to the smallest enterprises - so that experienced trades people, farmers and teachers, among others, can put their skills to good use."
"This is critical to offering, hope, safety and dignity to millions of refugees."