This study assesses the seismic performance of welded and bolted beam-to-column connections in a representative four-story steel building located in Cuenca, Ecuador. The global structure, comprising square tubular columns and I-shaped beams, was proportioned in accordance with NEC 2015 using the LRFD methodology and modeled in specialized finite element software. The design met both elastic and inelastic drift limits, with maximum inelastic story drifts of 1.4% in both principal directions. The most critical connection, located at the first story under the fifth LRFD load combination, was analyzed in detail using nonlinear FEM simulations. Four welded (W1–W4) and four bolted (B1–B4) connection alternatives were developed. Configurations W1–W3 and B1–B3 exceeded code limits due to excessive plate strain, weld utilization, or bolt demand. In contrast, W4, incorporating symmetrical internal stiffeners, reduced plastic strain by 9% and weld utilization by over 40%. B4, featuring an 8 mm-thick column and 12 mm reinforcement plates, lowered von Mises stress to 26.9 MPa and bolt utilization by 17%. Both W4 and B4 satisfied the requirements established by the design code. The results highlight the effectiveness of targeted reinforcement and moderate increases in column thickness for enhancing joint performance, offering a practical solution for achieving code-compliant connections in seismic-prone steel structures.