The excited-state dynamics of Fe(III) tetrakis(4-hydroxyphenyl)porphyrins were investigated on a femto- to nanosecond time scale. In acetonitrile solution, the porphyrin excited state relaxes back to the ground state in less than 30 ps. The excited-state lifetime increased to over 2.5 ns in electropolymerized films. A similar effect is observed when porphyrins are incorporated into a PMMA polymer film. The excitation is localized on a single porphyrin chromophore in all systems, but the relaxation pathways differ in solution and solid state. The increase of the excited-state lifetime is attributed to changes in vibrational modes, such as doming of the macrocycle, induced by the steric demands of the solid-state environment.