Vibrational dephasing of the overtone bands of chloroform and its deuterated analogue has been studied by higher-order nonlinear spectroscopy. The overtone signals of v = 2 and 3 are based on the fifth-and seventh-order optical nonlinearity, respectively. The overtone vibrational dephasing signals as well as the fundamental ones are represented well by a single-exponential function. These dephasing signals are not explained by the stochastic theory with a time correlation function having a Gaussian or exponential character. Effects of resonant transfer and population relaxation are found not to be important for the deviation from the theoretical prediction. It is suggested that polyatomic natures of the molecule such as off-diagonal anharmonicity or coupling with combination bands may be responsible for this deviation.