This article reports the development of a novel embedded acoustic waveguide sensor concept for monitoring the curing process and online health of composite structures. A sleeved waveguide embedded in the composite is proposed to confine guided waves in one dimension, with leakage to the surrounding media only through specially created openings, thus enhancing the capability to inspect large structures. The method is first developed using a rectangular copper strip embedded in an epoxy plate structure having an artificial delamination-type defect. Finite element simulations are used to gain insights on parameters and limitations. The approach is also demonstrated on a more practical bi-layer composite plate with an artificial delamination and an embedded wire waveguide sensor. © 2017 The Author(s).