Tea anthracnose is one of the major diseases in tea cultivation in Japan. Since the leading cultivar ‘Yabukita’ is susceptible to the fungus, it is important to develop cultivars resistant to the disease. In the present study, 5 vegetative propagated lines as parents and F₁ lines from reciprocal diallel crosses were used as materials. Scores of 1 (no) to 5 (severe) were used to express the degree of disease infection. Diallel analysis was conducted using computer software “DIAL98” developed by Ukai (2002). Additive effect was highly significant, while the dominance effect was negligible. The value of broad and narrow sense heritability were very high, 0.947 and 0.943, respectively. There were no significant differences between the reciprocal crosses and between the replications. Epistasis was not recognized. The (Vr, Wr) graph indicated that ‘Sayamakaori’ harboured mostly dominant alleles, and ‘Yamatomidori’ mostly recessive alleles.