The use of advanced materials and structural systems for vibration control has grown significantly over the past decades. Innovative vibration-control devices such as Tuned Mass Dampers (TMDs), Tuned Liquid Column Dampers (TLCDs), and hybrid devices have been extensively studied and some of these have been successfully implemented in real structures. Meanwhile, the rise of 3D printing has opened new opportunities for vibration mitigation and various additive-manufacturing techniques and 3D printed materials have been employed to produce internal patterns that mitigate mechanical vibrations [1]. Among these, thermoplastic polyurethane (TPU) has emerged as a particularly promising material. In fact, devices in TPU have even been printed to reduce vibrations transmitted to the human body during motorcycle riding [2]. Despite significant progress in understanding the dynamic behaviour of 3D-printed materials, there remains a shortage of studies coupling advanced analytical treatments of the frequency response function (FRF) of multi-degree-of-freedom (MDOF) 3D-printed systems with experimental validation. To address this gap, the present work proposes a simplified approach for the dynamic characterization of viscoelastic 3D-printed specimens. The proposed approach combines an evolutionary optimization algorithm using a genetic algorithm with an analytical formulation extending single-degree-of-freedom (SDOF) viscoelastic FRF theory [3] to MDOF systems. To assess the reliability of the proposed approach, several dynamic tests have been conducted in the Experimental Dynamics Laboratory at the University of Palermo. Specimens printed in TPU 85A featured varying heights, different internal patterns such as grid, honeycomb and gyroid and different infill percentages. Results show that the proposed approach accurately identifies the dynamic properties of the specimens and the FRF reconstructed from the simplified analytical model using the parameters obtained via genetic-algorithm optimization exhibits excellent agreement with the experimentally measured FRF.