This paper studied external-source-excited vibration response of double-bay multi-storey building frames for the effect of joint stiffening on bending moment and joint displacement. One of the frames has normal rigid joints. Three others of the frames have stiffened joints of stiffened lengths: 275mm, 425mm and 775mm respectively. Lumped mass system was the dynamic model adopted. The frames were modeled as those with flexible horizontal members, permitting rotation of joints and having multi degrees of freedom (MDOF). Classical displacement method of analysis was adopted using fixed end reactive moments which were modified to include the contributions of joint stiffening. The study revealed that stiffening of joints results in: (i) decrease in displacements at the joints; (ii) substantial reduction in deflection and significant increase of deflection ductility and energy ductility of flexural members. (iii) increase in joint moments and decrease in span moments.