The prominent third-order nonlinear optical properties of ${\mathrm{WTe}}_2$ films are studied through the Z-scan technique using a femtosecond pulsed laser at 1030 nm. Open-aperture (OA) and closed-aperture (CA) Z-scan measurements are performed at different intensities to investigate the nonlinear absorption and refraction properties of ${\mathrm{WTe}}_2$ films. OA Z-scan results show that ${\mathrm{WTe}}_2$ films always hold a saturable absorption characteristic without transition to reverse saturable absorption. Further, a large nonlinear absorption coefficient $\beta$ is determined to be $3.37\times {10}^3\mathrm{cm}/\mathrm{GW}$ by fitting the OA Z-scan curve at the peak intensity of $15.603\mathrm{GW}/{\mathrm{cm}}^2$. In addition, through the slow saturation absorption model, the ground state absorption cross section, excited state absorption cross section, and absorber’s density were found to be $1.4938\times {10}^{16}{\mathrm{cm}}^2$, $1.2536\times {10}^{16}{\mathrm{cm}}^2$, and $6.2396\times {10}^{20}{\mathrm{cm}}^3$, respectively. CA Z-scan results exhibit a classic peak–valley shape of the CA Z-scan signal, which reveals a self-defocusing optical effect of ${\mathrm{WTe}}_2$ films under the measured environment. Furthermore, a considerable nonlinear refractive index value $n_2$ can be obtained at $1.629\times {10}^2{\mathrm{cm}}^2/\mathrm{GW}$. Ultimately, the values of the real and imaginary parts of the third-order nonlinear s