Soybean mosaic potyvirus (isolates S1 and P1) caused significant reduction in plant height, number of pods/plant, pod length, number of grains/pod and 100 grains weight in mechanically inoculated eight soybean varieties. The reduction in plant height of varieties Recondita, Ajmiri, Kingsay, Weber-84, Swat-84, Epps, Malakand-96 and Kharif-93 due to S1 isolate was 14.9, 15.2, 9.5, 11.0, 45.0, 14.5, 5.2 and 21.1 %, respectively. While in case of P1 isolate the reduction was 6.3, 29.5, 6.0, 47.6, 34.4, 26.2, 1.8 and 15.8 %, respectively. Analysis of variance of the yield components indicated that both isolates (S1 and P1) caused a significant reduction in pod length of all eight varieties. A 4.2 to 23 % reduction occurred in pod length due to S1, while 5 to 24 % reduction was observed in case of P1 isolate. Isolate S1 caused 1.5 to 68.6 % and P1 6.6 to 31.1 % reduction in number of pods per plant. SMV-S1 and P1 caused significant reduction in number of grains per pod. However, the percent reduction due to S1 was 4.8 to 24.7 %, while reduction due to P1 was 10.5 to 29.3 %, respectively. Both isolates affected the weight of grains significantly. The percent reduction was 5.3 to 21.7 and 7.3 to 20 due to SMV-S1 and P1 isolates, respectively.