Until now, studies have shown that stresses on the plane (y-z plane) perpendicular to the circumferential direction (x-axis) of an O-ring do exist. Stresses on the planes (x-y plane and x-z plane) parallel to the circumferential direction of the O-ring have not been reported to exist. In this study however, it is demonstrated through a 3-dimensional stress analysis that stresses on the x-y plane and x-z plane of the O-ring under uniform squeeze rate and internal pressure do exist. Therefore, to study effectively 3-dimensional stress distributions of an O-ring under these loadings, stress distributions of every plane should be analyzed. This study develops a photoelastic experimental hybrid method to analyze 3-dimensional stress distributions of an O-ring under uniform squeeze rate and internal pressure, and uses it to determine the stress distributions in every plane, including the Von Mises equivalent stresses, at any arbitrary point of the O-ring under uniform squeeze rate and internal pressure.