We present a new process to form superstable foams with hydrophobically modified cellulose (HMC) microparticles. The microparticles were formed by a water-based liquid-liquid dispersion mechanism, in which the hydrophobic cellulose dissolved at high pH was sheared and precipitated in acidic aqueous media. The resulting cellulose particles immediately adsorbed onto the water/air interfaces created during shear blending, which formed particle-stabilized foams with exceptional long term stability. We investigated how parameters, including pH and cellulose chemistry affect the particle formation and resulting foam properties. The particle surface analysis indicated that the long term loss of foamability is associated with molecular reconfiguration of the particle surface. This new class of organic solvent-free, non-toxic, cellulose-based particle stabilizers could form the basis of new biodegradable products for the food, personal care, and pharmaceutical industries.