Iron oxide particles are presented to be a promising reinforcement to increase the mechanical properties of 3D printing acrylonitrile-butadiene-styrene (ABS) matrix composite filaments. 2D- and 3D- Finite Element Method (FEM) micromechanical models are developed to predict the deformation behavior and observe the distribution stress surrounding filler particles. Iron oxide particle geometry with an average size of 45 micron and the cross-sectional microstructure of the ABS composite filaments were observed by Scanning Electron Microscopy (SEM) for constructing the modeling. The highest stress presented surrounding the iron oxide particles was around a 14% increase compared to the ABS matrix. The predicted stress-strain curves were compared with the experimental results from nanoindentation measurement. The stress-strain curves differed depending on the morphological shape and size of iron oxide particles. The present work reveals the effect of irregular shape on the local stress distribution near the reinforcing particle to describe the tensile and hardness properties of the composite filaments.