The severity of major depressive disorder (MDD), which is related to the depressive symptoms, is a predictor of clinical outcomes and may be used to determine the appropriate treatment. However, there is a lack of systematic research on the relationship between early depressive symptoms and MDD severity. This study aimed to clarify the association between initial depressive symptoms and MDD severity in working patients. We assessed 118 patients aged over 20 years who visited the Neuropsychiatry Department of the Osaka City University Hospital following their first episode of MDD. Logistic regression analyses were performed to estimate the odds ratios (OR) with 95% confidence intervals (CI) for the associations between age, gender, marital status, working hours, and initial self-perceived depressive symptoms and MDD severity. Age and working hours were analyzed as continuous variables, and gender (man, woman), marital status (married, single) and severity (mild to moderate MDD, severe to very severe MDD) were analyzed as categorical variables. The most common initial self-perceived symptom was "depressed mood," followed by "fatigue or loss of energy nearly every day." The univariate analysis found no association between age, gender, marital status, or working hours and MDD severity. Initial self-perceived non-somatic symptoms were associated with increased odds of having severe MDD (odds ratio = 3.32, 95% confidence interval 1.46-7.58), and this association persisted in the adjusted model (odds ratio = 3.35, 95% confidence interval 1.47-7.60). Initial self-perceived non-somatic depressive symptoms are significantly associated with MDD severity at its first onset. Workplace support may lead to the early detection and treatment of working patients with non-somatic symptoms.