The performance of fabric with lime mortar (LM) as the cementitious matrix was investigated for the strengthening of lime masonry wallettes, which were compared with the respective cement-based matrix. Based on the material composition identified at selected heritage sites, a set of 54 clay brick–LM masonry assemblages were constructed and strengthened using glass fabric and two different grades of the cementitious matrix. Diagonal, four-point bending, and column uniaxial compression tests were performed to evaluate the shear, flexural, and axial behavior of the strengthened lime masonry specimens. The test results show that the fabric with compatible mortar could be used to improve the strength and ductility of old lime masonry structures. In addition, the experimental results were compared with the respective theoretical predictions estimated using the available analytical models.