Additive manufacturing (AM) enables the production of lattice structures with unique properties using different production techniques. In this way, it is possible to obtain the desired mechanical properties by using different production parameters and lattice geometries. In this study, the load behaviors of the octet-truss lattice structure produced by fused deposition modeling (FDM) method with different transition geometries were investigated. Compression tests were carried out on lattice structures and also finite element method (FEM) was performed to determine the stress distributions and deformations. According to the results, it was observed that the transition geometry is an important parameter on the deformation patterns and stress distributions. In the lattice structure without transition geometry, plastic deformation occurred at low-stress values while the transition geometries exhibited plastic deformation at high-stress values. In addition, the effects of the transition geometries on the deformation types were observed. The deformation area on the samples having straight and inclined-transition geometries affected less area than the sample without transition geometry. It was found out that the stretch-dominated deformation type, which significantly affects the strength of the lattice structures subjected to load, was formed in all lattice structures.