A lens module includes a lens holder and a lens. The lens holder comprises a through-hole. The lens holder comprises an inner wall surrounding to define the through-hole. A first thread is formed on the inner wall. A second thread is formed on an outer sidewall of the lens. The first thread cooperates with the second thread to fix the lens on the lens holder. At least one first slot is defined on the outer sidewall of the lens and around a periphery of the lens, and a seal ring is received in each first slot. At least one second slot is defined on the outer sidewall of the lens along a direction of an optic axis of the lens. Each second slot passes through each first slot to form a receiving space. The disclosure also provides an electronic device having the lens module.