In this study, a multifunctional, hierarchically modified glass fiber-reinforced polymer composite laminate (GFRP) capable of harvesting thermoelectric energy is fabricated and demonstrated. The fibrous reinforcements were hierarchically patterned with alternate n- and p-type graphene nanotube (single-walled carbon nanotube - SWCNT) aqueous dispersions, which were printed via ink dispensing processes. The optimal n- and p-type resin-impregnated printed films demonstrate high power factors of 82 and 96 μW m⁻¹ K⁻², respectively, and excellent stability in air. The manufactured GFRP-based graphene thermoelectric generator (GTEG) has the capability to stably function up to 125 °C under ambient conditions (1 atm, RH: 50 ± 5% RH). Printed SWCNT-based thermoelectric (TE) modules were successfully designed and fabricated onto a glass fiber fabric substrate with remarkable properties of n-type and p-type TE thin films resulting in exceptionally high performance. The thermoelectrically functionalized GFRP exhibits excellent stability during operation with obtained TE values of an open circuit voltage V_OC = 1.01 V, short circuit current I_SC = 850 μA, internal resistance R_TEG = 1188 Ohm, and a generated power output P_max = 215 μW at ΔT = 100 °C with T_C = 25 °C. The novelty of this work is that it demonstrates for the first time a multilayered hierarchically modified carbon-based energy-harvesting structural composite, capable of powering electronic devices such as a LED light from the power it generates when exposed to a temperature difference, and the overall results are among the highest ever presented in the field of energy-harvesting structural composites and printed carbon-based thermoelectrics. Both experimental measurements and simulations validated the TE performance. In addition, GFRP-GTEG showed a bending strength of 310 MPa and a flexural modulus of 21.3 GPa under room temperature (RT) and normal conditions (25 °C), retaining to a significant extent its mechanical properties while simultaneously providing the energy-harvesting capability. The aforementioned functional composite may be easily scaled-up, delivering potential for industrial-scale manufacturing of high-performance TEG-enabled structural composites.