Composite structures have wide applications in mechanical fields. Such structures consist of several joints, which may run a risk of eventually weakening a structure in case of excessive weight. It is, therefore, necessary to strengthen a structure so as to reduce the chance of failure. The present study was undertaken with a model of tubular T-joint having adhesive fillet. It also focussed on three-dimensional stress analysis on adhesive fillet. The model was made of laminated fibre-reinforced polymer (FRP) composite tubes with adhesive triangular fillet, subjected to axial compressive loading. The modelling and analysis were carried out by using finite element method (FEM) for three different joints with different geometrical parameters. The model was validated by using the available finite element model results. Based on the present finite element model results, the axial stress (σz) at brace-fillet intersection, circumferential stress (σφ) and circumferential-axial stress (τφr) at chord-fillet intersection were found to have greater effect as compared with other stress components. The maximum value of stress component could be noticed in between the brace and the chord joint region, which could eventually cause failures. The effect of adhesive fillet on deflection was studied in details by using ANSYS 18.1, and results showed that deflection of adhesive fillet model could be reduced by 12.36% as compared with non-fillet condition. Based on the present research findings, the presence of adhesive fillet was found to significantly reduce deflection effect as well as improve joint strength and stability of the structure.