Charge-4e superconductivity as a novel phase of matter remains elusive so far. Here, we show that charge-4e phase can arise as a vestigial order above the nematic superconducting transition temperature in time-reversal-invariant nematic superconductors. On the one hand, the nontrivial topological defect-nematic vortex-is energetically favored over the superconducting phase vortex when the nematic stiffness is less than the superfluid stiffness; consequently the charge-4e phase emerges by proliferation of nematic vortices upon increasing temperatures. On the other hand, the Ginzburg-Landau theory of the nematic superconductors has two distinct decoupling channels to either charge-4e orders or nematic orders; by analyzing the competition between the effective mass of the charge-4e order and the cubic potential of the nematic order, we find a sizable regime where the charge-4e order is favored. These two analyses consistently show that nematic superconductors can provide a promising route to realize charge-4e phases, which may apply to candidate nematic superconductors such as PbTaSe_{2} and twisted bilayer graphene.