A study was carried out to investigate the effects of plain and 3/1 twill weave designs on the tensile strength of polyester-cotton blended fabrics. For this purpose five fabric samples, each of plain and twill designs, were made on projectile weaving machine from 15 tex polyester-cotton (52:48%) yarn. The fabric count was increased from 80 (40+40) to 160 (80+80) with equal increment of 10 threads per 25mm both in warp and weft directions to obtained fabrics of different weights. After enzymatic desizing, tensile strength of fabric samples was determined as per standard test method. Comparison of test results shows that plain fabric samples have considerable high tensile strength as compared to twill fabric samples at the same fabric counts.