Collisional mixing among the z(3)D(J) and z(3)F(J) states of Fe[3d(6)4s(a(4)D)4p] atoms was investigated in He and Ar by laser-induced fluorescence method. The z(3)D(J) and z(3)F(J) states of Fe atoms were generated directly by photodissociation of Fe(CO)(5) followed by single photon absorption within a laser pulse using an unfocussed laser beam with atomic transition frequencies of Fe. When the z(3)D(3) level was excited, the emissions from this level showed a double exponential decay. The fast and slow components of the decay constants from the z(3)D(3) level were 10.7X10(-10) and 0.3X10(-10) cm(3) molecule(-1) s(-1) in He, and 8.8X10(-10) and 1.6X10(-10) cm(3) molecule(-1) s(-1) in Ar, respectively. When the z(3)F(4) level was pumped, the emissions from this level showed a single exponential decay and the decay constants were the same as those of the slow components of z(3)D(3). The emissions from higher-lying levels were single exponential at low pressures and the decay constants were in the range of 0.7-3.6X10(-10) cm(3) molecule(-1) s(-1). It is found that the collisional mixing between the z(3)D(3) and z(3)F(4) levels is very fast in both buffer gases while the mixing among the higher-lying four levels is relatively slow. The radiative lifetimes of the z(3)D(J) and z(3)F(J) levels were 280-370 and 770-1100 ns, respectively, depending on J. Kinetic simulations of time profiles from the laser excited and collisional product levels revealed that intermultiplet mixing appeared to be more efficient than intramultiplet mixing.