In the single-lap joint (SLJ) geometry, peel stresses occur at the overlap ends due to load eccentricity and the presence of shear-free adhesive termination surfaces. These peel stresses, along with the transverse tensile stresses which occur along the overlap longitudinal axes, and adhesive shear stresses, ultimately cause joint failure. Obviously, reductions in these stresses should result in higher joint strength and increased load capacity. In the present study, the mechanical behavior of the SLJ geometry of various widths having spew fillets, which was subjected to tensile loading, were investigated experimentally and numerically. For this purpose, firstly, four different types of SLJ samples (without spew fillet, with spew fillet at joint edges, with spew fillet at joint ends, and with spew fillet at all edges) were produced for experimental studies by using two-part paste adhesive. Then, stress analyses in the SLJ were performed with a three-dimensional non-linear finite element method by considering the geometrical non-linearity and non-linear material behaviors of both adhesive (DP460) and adherend (AA2024-T3). It was concluded that the spew fillet in the SLJ geometry with variable widths decreases stress concentrations and increases the load carrying capacity of the joint.