<p>Tomato spotted wilt virus (TSWV) is distributed all over Japan and globally, seriously damaging infected plants. A resistance-conferring gene, <i>Tsw</i>, that controls the yellow spotted wilt disease in bell pepper (<i>Capsicum annuum</i>) plants caused by TSWV infection in Japan, is now commercially available. In this study, we isolated for the first time in Japan, a resistance-breaking isolate, TSWV-JRB, from bell pepper plants harboring <i>Tsw</i>. The virus overcame the resistance conferred by <i>Tsw</i> in its heterozygous and homozygous configurations. The host range or virulence of TSWV-JRB and one of the non-resistance breaking isolates from Japan did not differ, except in the plants harboring <i>Tsw</i>. The TSWV-JRB acquisition rates and transmission rates of the thrip pests <i>Frankliniella occidentalis</i> and <i>F</i>. <i>intonsa</i> were 93% 38%, and 78% and 38%, respectively<i>.</i> A phylogenetic analysis of the <i>N</i> gene sequences indicated a distant relationship between TSWV-JRB and other Japanese isolates but a close association with Asian and European isolates. A comparison of the amino acid sequences encoded by these resistance-breaking and non-resistance-breaking <i>NS</i>s suggested that a residue 74 (S→P) is a putative resistance breaking-associated substitution. This is the first study to report <i>Tsw</i>-induced resistance breaking by TSWV in Japan. These results indicated the presence of a novel substitution in TSWV that might contribute to <i>Tsw</i>-resistance breaking.</p>