Several studies have reported that not only patients with chronic diseases but also their partners are likely to face major psychosocial problems. This study examined the association between a partner’s ongoing treatment for chronic disease and the risk of psychological distress after the Great East Japan Earthquake (GEJE). In 2012, a questionnaire was distributed as part of a cross-sectional study of participants aged 20 years or older living in a municipality that had been severely inundated by the tsunami following the GEJE. We identified couples using the household numbers of the municipality and collected self-reported information on ongoing chronic disease treatment for stroke, cancer, myocardial infarction, and angina. Psychological distress was evaluated using the Kessler 6 scale (K6) and was defined as a score ≥ 5/24 points. Among 1,246 couples (2,492 participants) thus identified, 2,369 completed the K6. The number of participants whose partners were under treatment for chronic diseases was 209 (9%). Overall, participants with partners who were receiving treatment for chronic diseases (odds ratio [OR] = 1.3, 95% confidence interval [CI] = 0.95-1.8, P = 0.09) did not show a significantly higher risk of psychological distress using logistic regression analysis. Women, but not men, whose partners were receiving treatment for chronic diseases, had a higher risk of psychological distress (women: OR = 1.6, P = 0.02; men: OR = 1.0, P = 0.92). After the GEJE, only in women the presence of partners under treatment for chronic diseases appears to be a risk factor for psychological distress.