In this paper, the main goal is to characterize the designed triply periodic minimal surfaces (TPMS) based scaffolds in different porosities and assess the effect of the design, porosity, and biodegradation on the mechanical properties of the scaffolds. The mechanical properties of the TPMS designs were compared for different porosities to assess the impact of design and porosity on the mechanical strength. In addition, the effects of biodegradation on the mechanical properties and the failure patterns of the designs were investigated after six months of biodegradation. The scaffolds were manufactured using the fused deposition modeling (FDM) technique and polylactic acid (PLA) filament. The results indicated that the Gyroid scaffolds maintained their mechanical strength and apparent modulus with the increase in the design porosity. Six months of biodegradation depleted the mechanical properties of the structures with Schwarz-D design much more than the Gyroid scaffolds, and the Gyroid structures with different porosities kept their mechanical strength in the same range. Also, the results demonstrated that the biodegradation transformed the ductile failure behavior of the TPMS scaffolds to brittle. The results of this study deliver an advanced understanding of the effects of TPMS designs, porosity, and biodegradation on the mechanical properties of the scaffolds.