A brake mechanism is applied to a stroller. The stroller comprises a first wheel. The first wheel has a first hub. The brake mechanism comprises a first wheel base, a ratchet, an operating member and a first engaging member. The first wheel is pivotally connected to the first wheel base. The ratchet is pivotally connected to the first wheel base. The ratchet comprises a plurality of first and second engaging teeth arranged interlacedly. The operating member is pivotally connected to the first wheel base and abuts against the ratchet. The first engaging member is pivotally connected to the first wheel base. When the operating member is pressed to drive the ratchet to rotate, the ratchet drives the first engaging member to move, so that the first engaging member is capable of selectively engaging with one of the first or second engaging teeth.