Dermatomyositis (DM) is an autoimmune inflammatory disease characterized by skin eruptions and myositis. Anti-transcriptional intermediary factor 1-γ antibody (anti-TIF1-γ Ab) is one of the most frequently detected myositis-specific autoantibodies and adults positive for anti-TIF1-γ have markedly higher rates of malignancy. Our aim was to determine the clinical associations of anti-TIF1-γ levels in 31 Japanese adult DM patients positive for anti-TIF1-γ. We determined associations between the anti-TIF1-γ index and patient characteristics and disease severities. Sixteen patients with anti-TIF1-γ Ab had concomitant malignancies. A mild positive correlation was found between the levels of serum creatine phosphokinase at the first visit and anti-TIF1-γ levels. In contrast, there was no significant difference in the anti-TIF1-γ Ab index between patients with and without malignancy. Dysphagia tended to be observed in patients with malignancy. On sequential analysis, anti-TIF1-γ levels in patients without malignancy were lower or turned negative after treatment for DM. Ab titers tended to be sustained in patients with stage IV malignancies. Interestingly, a re-increase in the Ab titer was observed on recurrence of malignancy or increase in DM activity. Four patients were completely cured of their malignancies, and anti-TIF1-γ levels in three patients turned negative with the loss of DM activity. These data suggest that higher anti-TIF1-γ titers may not directly indicate the presence of malignancy. Nevertheless, longitudinal changes in the anti-TIF1-γ index in individual patients may partially reflect activities of both DM and malignancy.