Phenolic foams have numerous applications in transportation, building and packaging industries. They have very interesting properties such as low density, good fire properties and challenging thermal and mechanical performance. However phenolic foams based on phenol and formaldehyde are currently controversial because of their carcinogenicity. Therefore, new phenolic foams based on non-toxic biobased molecules such as tannins (4th component in the biomass after cellulose, hemicellulose, and lignin) have prominent research attention. These molecules can react with hexamine, a non-carcinogenic reactant, in acid catalysis and create thermoset tridimensional networks. By hence, this work presents a new bio-based formulation of mimosa tannin-based foam that is shaped via a new chemical foaming process using a non-toxic and an available foaming agent. A novel microstructure is obtained due to the chemical foaming process used. This microstucture is characterized and is related to mechanical properties.