Mason’s nonlinearity constants D [W. P. Mason, in Physical Acoustics, edited by W. P. Mason (Academic, New York, 1965), Vol. IIIB, Chap. VI] in GaAs at 298 K have been estimated from second‐ and third‐order elastic constants along the , , and  directions for longitudinal and shear waves. These values are further used to estimate the frequency dependence of the ultrasonic attenuation in the range 40–640 MHz and are found to be in good agreement when compared with experimental values available in the literature. Previously, it was established that phonon‐phonon interactions produce a drag on moving dislocations in a solid. In the present work, the drag coefficients for edge and screw dislocations along the  and  directions in single‐crystal GaAs have been estimated from the evaluated nonlinearity constant D values at 298 K. We have also estimated the values of Breazeale’s nonlinearity parameters β [M. A. Breazeale and J. Philip, in Physical Acoustics, edited by W. P. Mason and R. N. Thurston (Academic, New York, 1984), Vol. XVII, Chap. I] along the , , and  directions and found them to be consistent for the three principal orientations, compared with the results for other samples. It is pertinent to note that the mode Grüneisen number γ ji involved in the estimation of Mason’s nonlinearity constant D is deceptively similar to Breazeale’s nonlinearity parameter β. The nonlinearity constant D is evaluated from knowledge of the Grüneisen number γ ji for various modes and directions, whereas Breazeale’s nonlinearity parameter β is the negative ratio of coefficients of nonlinear term to the linear term of the (dissipationless) nonlinear wave equation for pure mode directions. Both D and β, in general, are temperature dependent.