Invoking defects with ion implantation is an attractive means to modify the physical parameters of materials. In the present work, Cu ions at fluence (1 ${\times}$ 10$^{15}$ ions cm$^{-2}$) with 100 keV energy were implanted on BiSbTe$_3$ (BST) single crystals. The X-ray diffraction (XRD) measurements on pristine and Cu ion-implanted crystals demonstrate a decrease in lattice parameter (a = b) from 4.31 to 4.26 A$^º$ with an increment in ‘c’ lattice parameter from 30.47 to 30.48 A$^º$ with implantation. The peaks in XRD are shifted to lower 2${\theta}$, which are attributed to tensile strain induced in sample due to implantation. The composition of pristine BST crystal depicted from X-ray photoelectron spectroscopy is Bi:Sb:Te = 1.08:1.45:2.4. The implantation of Cu in BST single crystals is confirmed by energy dispersive X-ray technique. The resistivity measurements reveal a decrease in resistivity with implantation due to decrease in strain with Cu ion implantation. The Hall coefficient is found to be positive for both the samples signifying that the holes are the dominating charge carriers. A slight shift in Fermi level was observed with implantation. The magnetoresistance data is fitted with an equation $R(B)$ = c+b${\times}$B$^a$ using Python. The parameter c varies from ${\sim}$228 to ${\sim}$388.5 m${\Omega}$ for the pristine sample, whereas for implanted sample it varies from 5.89 to 6.66 m${\Omega}$ throughout the temperature range ${\sim}$4–300 K. This drastic reduction in c is due to the Cu ion implantation, which augments the metallic nature of the sample.