Understanding the dynamic behavior of structures under various types of loads is essential for ensuring the safety and durability of buildings, especially in seismically active regions. Natural frequencies and corresponding mode shapes are key dynamic properties that influence a building’s response to environmental excitations such as earthquakes, wind, and operational vibrations. When the excitation frequency approaches the natural frequency of a structure, resonance may occur, potentially leading to excessive deformations or structural failure. Therefore, accurately determining these dynamic characteristics is crucial for both design and retrofitting purposes. Composite structures, comprising steel frames and concrete walls or slabs, are increasingly utilized in modern construction due to their combined strength, stiffness, and energy dissipation capacity. Despite their advantages, the modeling of such structures is challenging due to the nonlinear material behavior and the complex interactions between steel and concrete elements. Analytical methods often fall short in capturing these complexities, making numerical simulation techniques such as the Finite Element Method (FEM) essential. In this study, a five-story steel-concrete composite building is modeled and analyzed using Abaqus software. Modal analysis is performed to identify natural frequencies and mode shapes. Furthermore, the research includes a mesh sensitivity study, the implementation of I-beam sections to enhance model realism, and a comparative discussion with theoretical formulations. These efforts aim to improve the accuracy, applicability, and engineering relevance of vibration analysis in mid-rise structures.