The current study focuses on the experimental investigation of an integrated seismic/energy upgrading system comprising a textile-reinforced mortar (TRM) overlay combined with extruded polystyrene (XPS) boards. TRM is a proven strengthening/rehabilitation technique for both masonry and concrete structures comprising externally bonded fibrous girds by means of inorganic binders. XPS is a closed-cell polymeric foam that is widely used as insulation of reinforced concrete elements and masonry infills. The integrated TRM-XPS system in question is investigated herein in conjunction with masonry substrates. In this work, TRM consists of two layers of a dry carbon fiber textile embedded in a fiber-reinforced, polymer-modified cementitious mortar; the latter is the commercial product typically used as the adhesive mortar to bond and render XPS insulation boards (“XPS adhesive”). XPS boards are 20 mm thick. Material characterization tests include: (1) uniaxial tensile tests on TRM prismatic coupons; (2) single-lap/single-prism shear bond tests on TRM/masonry and TRM-XPS/masonry joints (XPS positioned either in between the TRM and the substrate or on top of the TRM); and, (3) concentric compression tests on perforated clay brick wallettes furnished with unilateral TRM jackets. It is concluded that: (i) the “XPS adhesive” is suitable for use as matrix in TRM qualifying as strain-hardening composites; (ii) bond-wise (when this type of composite is used as externally bonded reinforcement), the weak link is the “XPS adhesive” resulting in interlaminar shear failure regardless of the position of the XPS board in respect to the TRM; and (iii) the compressive strength of wallettes increases by up to 22% when unilaterally reinforced with TRM jackets.