This paper describes the adsorption of lead and cadmium ions from an aqueous solution using a composite of titanium dioxide (TiO2)-incorporated polyacrylonitrile (PAN) electrospun nanofibers. Adsorption capacities and the mechanical response of the PAN/TiO2 composite electrospun nanofibers are investigated at different weight percentages of TiO2 (0.5, 1.0, 2.0, and 5.0 wt.%). The adsorption capacities of the composite PAN/TiO2 (2.0 and 5.0 wt%) for Pb(II) and Cd(II) are remarkably increased by approximately 114 and 47%, respectively, compared to those of pure PAN electrospun nanofibers. Moreover, the adsorption of Pb(II) and Cd(II) by PAN/TiO2 nanofibers reaches an equilibrium within 60 min, and the process can be described using the nonlinear pseudo-second-order kinetic model. The adsorption isotherm study can be represented by the Langmuir model, which suggests the homogeneous distribution of monolayer adsorptive sites on the composite nanofiber surface. Furthermore, the ultimate tensile strength and ductility of all nanofiber membranes are measured through a uniaxial tension test. Mechanical tests reveal a reduction in the tensile strength of the PAN/TiO2 composite nanofibers with increase in TiO2 amount due to the possible formation of agglomerates and voids in the nanofiber structure.