Acrylonitrile-butadiene-styrene/nickel chloride (ABS/NiCl2) composites are prepared using the casting method. Structure of these composites is investigated by XRD and FTIR spectroscopy. XRD measurements revealed that the structural properties of ABS host polymer have been modified after doping with NiCl2. Various structural parameters such as crystallite size (D), lattice strain (ε) and dislocation density (δ) are estimated. ATR-FTIR spectra exhibited a clear change in the intensity and position of some of the main bands of the ABS polymer such as, Ni(OH)2, C ≡ N, C = O and C = C which confirms the interaction between ABS terpolymer and NiCl2. Coats–Redfern approach has been applied to explore the effect of NiCl2 on the kinetics of thermal degradation of pure ABS and ABS/NiCl2 composites. The results showed that the activation energy of every thermal degradation stage increases with increasing NiCl2 content confirming that the thermal stability of ABS/NiCl2 composites has been enhanced. The optical parameters such as Urbach energy (EU) and bandgap energy (Eg) are investigated in terms of the absorption coefficient. The dispersion parameters such as, oscillator energy (E0), dispersion energy (Ed), transition moments (M− 1 and M− 3) and oscillator strength (f) are evaluated by applying the single oscillator model (SOM). Effect of NiCl2 on the linear/nonlinear optical (NLO) parameters is investigated. Our results clearly revealed that doping ABS with NiCl2 improved the nonlinear optical properties, which are preferred for optoelectronic device applications.