To prevent disaster in future earthquakes, one way of retrofitting the members in reinforced concrete buildings is concrete jacketing. The present study investigates the effect of jacketing on the flexural strength and performance of beams. First, slant shear tests are conducted to study the interface between old and new concrete. Second, beam specimens are tested to study the effect of jacketing on the positive bending of the span region. Third, beam-column-joint sub-assemblage specimens are tested to study the effect of jacketing on the positive bending of the beams adjacent to the joint. Further, analytical investigations are carried out to predict the experimental results. A layered approach is used for the prediction of the moment versus rotation curves for the retrofitted beam specimens. An incremental nonlinear analysis is adopted to predict the lateral load versus displacement behaviour for the retrofitted sub-assemblage specimens. Finally, guidelines are provided for the retrofitting of beams by concrete jacketing.