This paper deals with the analysis of sandwich T-joints in terms of buckling loads, which are used in marine applications. Buckling loads have been investigated experimentally and numerically. Loading is applied as uniform axial compression. The GRP/PVC sandwich composite T-joints have been manufactured in six different geometries. Numerical and experimental results both show that the geometry of the T-joint area affects the buckling loads. It has been observed that failure mode is the same in all of the joint types, which is core shear. Stress distributions in T-joints have also been investigated under buckling loads and also for a constant compression load. It is seen that T-joint geometry has an effect on stress distributions obtained under buckling, loads.