Appropriate porosity is an important biomaterial design criterion for scaffolds used in tissue engineering applications as it can permit increased cell adhesion, migration, proliferation and extracellular matrix production within the scaffold at a tissue defect site. Tissue engineering scaffolds can either be injected in a minimally invasive manner or implanted through surgical procedures. Many injectable scaffolds are hydrogel-based; these materials often possess nanoscale porosity, which is suboptimal for cell migration and proliferation. Solid scaffolds with engineered micron-scale porosity are widely used, but these scaffolds are usually pre-formed and then must be implanted. Here we report on the development of a solid, injectable, biomaterial scaffold that solidifies in situ via phase inversion with microporous, interconnected architecture on the surface and within the bulk. This injectable system utilizes the biodegradable polymer poly(lactic-co-glycolic acid), a nontoxic FDA-approved solvent, and biocompatible porogens. Various scaffold formulations are examined in terms of morphology, porosity, degradation, elastic modulus, and ability to support cellular adhesion and growth. Furthermore, the ability to form a microporous architecture upon injection in vivo is verified. This technology is a promising noninvasive approach for in vivo formation of porous biodegradable scaffolds.