A secondary optical element including a light incidence surface, a light emitting surface, and a connecting surface is provided. The light incidence surface includes a first and a second light incidence surfaces. The first light incidence surface is a curved surface recessed toward the light emitting surface. The light emitting surface is opposite to the light incidence surface and includes a first and a second light emitting surfaces. The first light emitting surface is a free-form surface recessed toward the light incidence surface or a flat surface. The second light emitting surface is a free-form surface. A diameter of the second light emitting surface is larger than a diameter of the second light incidence surface, and the connecting surface is connected between the second light incidence surface and the second light emitting surface. A light source module is also provided.