This study shows an experimental method and a finite element model for modal analysis of 3D printed Polylactic acid (PLA) bolted joint beams. Three test samples are 3D printed with 20% infill density and tested with scanning head Laser Doppler Vibrometer (LDV) for its natural frequencies and mode shapes. The test specimens are a monolithic beam, a lap joint beam and a reduced Brake Reu β beam. Since the material properties like Young’s modulus and density of 3D printed structures are not exactly known, we develop a parameter estimation method to calculate these values. Using these estimated values, a prestressed nonlinear finite element model is created by taking the effect of friction in contacting interfaces. Ansys software is used to create the finite element models. The natural frequencies and mode shapes from experiment and finite element model match with an error less than 10%. This model and estimated parameters can be used for further studies with 3D printed polylactic acid material and in contacting interface modelling. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.