Switching magnetization via circularly polarized photons addresses fundamental questions of magneto-optical interactions between circularly polarized photons and magnetic materials, which enables the development of magneto-optical memory devices, such as all-optical magnetic recorder. Recently discovered 2D magnetic materials have offered a great platform to study the control of magnetic properties. Many experimental efforts have been focused on the control of magnetic properties using methods including application of an electric field, electrostatic doping, strain, pressure, etc. Controlling the magnetization without an application of external magnetic field has attracted much interests in the field of spintronics. Here, we present an all-optical helicity dependent control of magnetization in 2D atomically thin CrI₃. Our results allow for a better understanding of the all-optical magnetization switching mechanisms and open up possibilities on all optical control of 2D magnet based ferromagnetic bits.