A carbazole-bound ferrocenium salt [i.e., (eta(6)-Carbazole) (eta(5)-cyclopentadienyl) iron hexafluorophosphate-FS] is proposed as an efficient photoinitiator for the cationic ring-opening polymerization of epoxides under air upon the exposure to a near-UV LED at 385 nm or a visible LED at 405 nm. When using this ferrocenium salt FS (0.2 wt%)/diphenyliodonium hexafluorophosphate or FS (0.2 wt%)/diphenyliodonium hexafluorophosphate/N-vinylcarbazole, final epoxide conversions of 55-66 % can be obtained after 800 s of irradiation at 385 or 405 nm. Reference cationic photoinitiators (i.e., diphenyliodonium hexafluorophosphate; 9-(4-hydroxyethoxyphenyl) thianthrenium hexafluorophosphate and triphenylsulfonium hexafluorophosphate) are unable to initiate the epoxide polymerization under the same conditions. The photochemical mechanisms for the formation of the initiating species are studied using steady-state photolysis, cyclic voltammetry, laser flash photolysis and electron spin resonance spin-trapping techniques. Molecular orbital calculations help to describe the absorption properties and the initiation step. The performance attained when using FS alone is really promising for applications under soft near-UV or visible light-emitting diode irradiation.