Dispensing device of washing agents for a dishwashing machine, of the type comprises a body (2) to be fastened to a surface or wall delimiting a washing tub, having at least a portion of said body (2) protruding inside the washing tub; said dispenser (1) has at least a tank (11) for containing a liquid washing agent, means for dosing and/or dispensing a dose of liquid washing agent, a filling port (10) through which the liquid washing agent can be introduced into the tank (11), and closing means (15) of the filling port (10).According to the invention, the closing means (15) are capable of at least two different operating positions, where in one position they are apt to receive the liquid washing agent and direct it or convey it to the filling port (10), in order to fill the tank (11).