A flexible microwave applicator and method of use thereof. The applicator includes a flexible, dielectric-containing compartment (e.g. temperature regulated water or oil) having a variable contour, tissue-engaging surface and an opposite non-tissue-engaging surface and an antenna array adjacent to a non-tissue-engaging surface. The antenna array includes at least one flexible printed circuit board having a front metal surface, a dielectric substrate, a back metal surface, a connection structure for connecting the antenna array to at least one external microwave device, at least one dual concentric conductor aperture on the front surface, and at least one microstrip feedline in communication with the dual concentric conductor aperture and the connection structure. The microwave applicator also includes flexible attachment material for placement over the antenna array and dielectric compartment to allow the microwave applicator to be attached to a subject like a garment which closely conforms to the anatomy portion to be heated. The flexible attachment material may be configured such that the microwave applicator is configured as an appropriately-shaped type of garment, for example, a vest, jacket, cap, hood, blanket, custom shaped conformal wrap, sleeve, or as a pair of shorts.