Numerical and experimental investigations are carried out to study the combined effect of rotation and support nonuniformity on the modal characteristics of circular thick disks. The laboratory experiments on stationary and rotating circular disks are conducted to investigate the effects of partial support conditions on the in-plane and out-of-plane vibration responses of annular disks with different radius ratios. Numerical results suggested that the nonuniformity of the support along the circumferential directions of the boundaries affects the modal characteristics of the disk along the in-plane and out-of-plane directions, while introducing additional coupling between the modes. Specifically, some of the frequency peaks in the frequency spectrum obtained under uniform boundary conditions split into two distinct peaks in the presence of a point support. The results show that the in-plane modes of vibration are comparable with those associated with out-of-plane modes and are contributing to the total noise radiation. The coupling between in-plane and out-of-plane modes is found to be quite significant due to the nonuniformity of the boundary conditions. The experimental study confirms the split in natural frequencies of the disk that is observed in the numerical results due to both rotation and support nonuniformity. The applicability and accuracy of the formulations is further examined through analysis of modal characteristics of a railway wheel in contact with the rail.