A scale-dependent model of nanobeams with large deformations is developed to investigate the influences of a geometric imperfection on the chaotic response of nanotubes. In order to comprehensively simulate the effects of being at nanoscales, a nonlocal strain gradient theory (NSGT) is utilised. To model a geometric imperfection, an initial deflection is taken into account for the nanosystem. Since the relative motion between the nanofluid and nanotube at the interface is not negligible, Karniadakis-Beskok assumptions are employed to incorporate the effects of this relative motion. Utilising an energy-work balance technique, the nonlinear governing equations are derived for the coupled motion of the nanofluid-conveying NSGT nanotube. Finally, the influences of the geometric imperfection on the motion response are analysed using a direct-time-integration approach and a Galerkin scheme.