An exemplary backlight module (3) includes a light source assembly (33) and a light guide plate (34). The light guide plate includes a side surface (341), a light emission surface (348) substantially perpendicularly to the side surface, and a first groove (342) defined at the side surface. The first groove fixedly accommodates the light source assembly. Because the light guide plate includes the first groove fixedly accommodating the light source assembly, if the backlight module is subjected to shock or jarring, the light source assembly is prevented from being impacted by the light guide plate. Therefore, the backlight module has high reliability.