Purpose: The applications of flax fibre-reinforced polymers are becoming widely prevalent, particularly in the industrial sector. Generally, damage in composite material represents one of the predominant behavioural phases. The present paper aims to characterize this phenomenon and its related mechanisms in flax/Elium laminate composite using both linear and nonlinear vibration testing. Methods: This study was based on vibration testing applied for two composite configurations, namely cross-ply and unidirectional. The bio-composite samples were processed by the liquid resin infusion technique. Linear vibration excitations were carried on using an impact hammer. However, the nonlinear ones were achieved using a shaker. Experimental tests were realised for virgin and damaged composites during tensile testing. Results: The results of linear measurements indicated a frequency shift towards lower frequencies as the damage rate increased. Nonlinear measurements allowed the determination of two nonlinear parameters: the first being an elastic nonlinear parameter associated with the frequency shift, and the second being a dissipative nonlinear parameter related to the damping shift. The results demonstrated that the nonlinear resonance method exhibited greater sensitivity to the presence of damage compared to the linear resonance method. Conclusions: This study leads to distinguish the effectiveness of the nonlinear resonance method as a non-destructive technique for monitoring the structural health of bio-composites.