In this paper, we study the free vibration characteristics of curvilinear fibre composite laminates exposed to hygrothermal environment. The formulation is based on the transverse shear deformation theory and it accounts for the lamina material properties at elevated moisture concentrations and thermal gradients. A 4-noded shear flexible quadrilateral plate element based on extended finite element approach is employed for the spatial discretization. The effect of a centrally located cut-out, modelled within the framework of the extended finite element method, is also studied. A detailed parametric investigation by varying the curvilinear fibre angles at the centre and at the edge of the laminate, the plate geometry, the geometry of the cut-out, the moisture concentration, the thermal gradient and the boundary conditions on the vibration characteristics is numerically studied and it is hoped that this detailed study will help the designers in optimizing such structures under dynamic situation. © 2015 Elsevier Ltd.