An optical imaging system includes a first lens having a concave image-side surface, a second lens having a concave image-side surface, and a third lens having a positive refractive power. The optical imaging system includes a fourth lens having a positive refractive power and a concave object-side surface, a fifth lens, a sixth lens having a positive refractive power, and a seventh lens having a concave object-side surface. The first lens to the seventh lens are sequentially disposed at intervals from an object side toward an imaging plane.