The article presents the results of studying the fatigue characteristics of skin–stringer joints (T‑samples) made of a polymer composite material subjected to random vibroacoustic loading with a wide spectrum. Experimental data were analyzed to determine the damage initiation and growth mechanisms, as well as the criterion and failure mode for samples with and without impact damages. The effect of impact damage on the fatigue characteristics of the test samples at different impact energies and vibroacoustic loading levels is demonstrated. The main patterns of the influence of defects on the fatigue characteristics are revealed, which can be used in the future in creating computational models for damage development in structures made of the polymer composite material under vibroacoustic loading.