Ceramic matrix composite airfoils for gas turbine engines are provided. In an exemplary embodiment, an airfoil includes opposite pressure and suction sides extending radially along a span. The pressure and suction sides define an outer surface of the airfoil. The airfoil further includes opposite leading and trailing edges extending radially along the span, the pressure and suction sides extending axially between the leading and trailing edges. The airfoil also includes a filler pack defining the trailing edge; the filler pack comprises a ceramic matrix composite material. Moreover, the airfoil includes a plenum defined within the airfoil for receiving a flow of cooling fluid, and a cooling passage defined within the filler pack for directing the flow of cooling fluid from the plenum to the outer surface of the airfoil. Methods for forming airfoils for gas turbine engines also are provided.