Temperature and laser energy dependencies of electron g-factors are investigated for the conduction band of In0.53Ga0.47As/In0.52Al0.48As quantum wells using the time-resolved Faraday rotation (TRFR) technique. We found that in- and out-plane g-factors are ∼−3.20 and ∼−3.50 at a temperature of 5 K for the 12-nm wide quantum wells in a tilted sample configuration of the TRFR measurement. A comparison between the experiment and the eight-band Kane model calculation shows that the thermal distribution and dilatational change of the energy gap play an important role in explaining the temperature dependence of optically measured g-factors. We also found that the measured g-factor is influenced by the laser wavelength, which clearly shows that detection energy is the one of the significant factors for determining the optically measured g-factor.