This study examines the vibrational performance of 3D-printed continuous fiber composite materials reinforced with three different reinforcement types: carbon, glass, and Kevlar fibers, using a Markforged Mark Two Desktop 3D printer. The fibers are embedded in the thermoplastic Onyx matrix at two volume fractions, 21 and 41%, to explore the influence of fiber content on dynamic mechanical behavior. The natural frequencies of seven composite variations were measured using a free vibration experiment and modal analysis. Results indicate prominent variation in the vibrational behavior in composites compared with unreinforced matrix, where carbon fiber composites exhibit the highest natural frequencies due to the superior stiffness, and Kevlar exhibits the highest damping behavior due to its excellent energy absorption. Fiber content also significantly influences the natural frequency for all fiber types, highlighting the direct relationship between fiber volume fraction, mass, and material stiffness. These findings provide valuable insights for optimizing composite materials in applications sensitive to vibration, such as aerospace and automotive industries. Future work will investigate additional fiber orientations and matrix materials to enhance composite performance.