AC susceptibility and DC magnetization measurements were performed to examine the effect of P substitution on the superconducting and critical properties of optimally doped PrOFe0.9Co0.1As superconductor. Although P substitution increases the superconducting phase fraction, the TC of the compound is found to decrease at a rate of ∼13 K/at%. The magnetic critical current density (JC) and irreversibility field (H*) for these compounds were measured, both of which were found to decrease dramatically with the increase in phosphorus substitution. © 2011 American Institute of Physics.