To reduce nitrogen (N) loss from vegetable fields with minimum labor, the effects of a single application of different types of controlled mineralizing acetaldehyde condensation urea (CM-CDU) fertilizer on crop yield and N uptake, nitrate leaching from the surface soil (0–20 cm) and N2O emission from the soil after two continuous croppings of a leafy vegetable (komatsuna, Brassica napa L.) were examined. The following four treatments were established in plastic containers filled with an Andisol: urea, CM-CDU-4, CM-CDU-10 at a rate of 30 g N m−2 and a control (no N fertilizer). The CM-CDU-4 and CM-CDU-10 treatments released 80% of N at 25°C in 30–60 and 90–140 days after fertilizer application, respectively. The yields for the two crops were 1.55, 1.55, 1.26 and 0.34 kg fresh weight m−2 in urea, CM-CDU-4, CM-CDU-10 and the control, respectively. The amount of total nitrate leaching was 3.4, 2.3, 1.2 and 0.3 g N m−2 from urea, CM-CDU-4, CM-CDU-10 and the control, respectively. The total amount of N2O emission from urea, CM-CDU-4, CM-CDU-10 and the control over two crops was 0.12, 0.06, 0.04 and 0.01 g N m−2, respectively. The emission factors were 0.7, 0.3 and 0.2 from the urea, CM-CDU-4 and CM-CDU-10 treatments, respectively. The N use efficiency of urea, CM-CDU-4 and CM-CDU-10 was 87, 85 and 59%, respectively. Among the examined fertilizers, we recommend CM-CDU-4 as best for komatsuna production after examining two continuous croppings with a single application.