The solubility of phenylphosphinic acid (PPA) was measured for the first time in supercritical carbon dioxide (SCCO2) at 313, 323, and 333 K with pressure ranging from 10-20 MPa using a dynamic flow technique. The solubility of PPA in neat SCCO2 ranged from 0.1 X 10(-5) to 18 X 10(-5) mol/mol. The influence of cosolvent, methanol, on solubility behavior was studied by measuring the solubility of PPA in SCCO2 + methanol medium (1 and 4 mol % methanol) at 313 and 323 K with pressure varying from 10-20 MPa. The highest solubility of PPA in the (SCCO2) + methanol mixture is 29.4 X 10(-4) mol/mol at 313 K and 20 MPa with a methanol composition of 4 mol %. The solubilities in neat SCCO2 were correlated using different semiempirical equations (Mendez Teja, Chrastil, and Bartle) with an average deviation of <10%. The solubility in the presence of methanol was correlated with four semiempirical/empirical models (modified Chrastil, modified Mendez Teja, Garlapati model, and Jouyban equation); among these models, Jouyban model resulted in better correlation with an average deviation of 5%.