In this paper, linear and nonlinear vibration analyses are carried out on flax fibre reinforced composites with and without an interleaved natural viscoelastic layer. Experimental analysis was done in a clamped-free configuration on two stacking sequences of composites, [0]8 and [02/902]s. The procedure consists on exciting the specimens with different amplitude levels for the first six bending modes. The dynamic properties as frequencies and damping factors were studied, and the results obtained were analyzed and compared. Then, the amplitudes of deformations were determined and discussed for the different excitation levels. The presence of the non-linearity generated by the viscoelastic layer was clearly identified by the shift observed in the values of natural frequencies and loss factors with increasing excitation levels. The linear and nonlinear, elastic and dissipative parameters were calculated and compared.