Reducing electromagnetic interference in electronic equipment is of great importance. This is normally accomplished by increasing the shielding effectiveness of the enclosure. In this study, shielding effectiveness is examined against enclosure material, joint geometry, and operating frequency. An experimental apparatus is designed and manufactured to aid in finding the suitable joint configurations and materials with high shielding effectiveness. Three groups of material, namely, metallic, filled polymers, and metalized filled polymers, are investigated. In addition to the choices of material, effect of joint configurations on shielding behavior are examined. Based on the experimental results, empirical relations are developed that relate shielding effectiveness to effective length, shape factor, and aperture dimensions of the joint structure. Finally, the best material and joint geometry among the investigated cases are presented.