Initial geometric imperfection plays a vital role in determining realistic buckling load of any structure. Thin cylindrical shells are prone to dimensional imperfection depending on the manufacturing processes and geometric parameters. In this work, S2 glass-epoxy thin composite cylindrical shells were fabricated using filament wound technology utilising tow-preg as the raw material. Tubes were inspected using digital machine to quantify the magnitude of initial imperfection on the diameter. Statistical standard deviation is utilised to arrive at realistic geometric imperfection of these tubes. The tubes were filled to different volumetric level with low modulus elastic fillers. Filled tubes were then experimentally subjected to uniform external pressure to arrive at their buckling load-carrying capability. Non-linear finite element (FE) modelling of these tubes with measured initial geometric deviations on diameter is carried out to predict external pressure buckling load of the filled tubes. Eigen affine mode with only first mode shape is used to define imperfections. Results of FE model match with the experimental data within an accuracy of 10%. This confirms that a non-linear FE modelling with measured initial imperfections predicts the behaviour of the filled tubes very realistically. © 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group.