We investigated the growth and the phenology in Chamaecyparis obtusa two-year-old seedlings grown under several controlled temperature conditions of the outdoor temperature altered by ±0.0°C, +1.0°C, +2.0°C and +3.0°C. The results showed that growth period were longer under the warmer conditions, because initiation of elongation were earlier and end of growth were later. There were a greater length of main shoot elongation and diameter of main shoot under +2.0°C and +3.0°C treatments, with a higher ratio of main shoot elongation and H/D ratio, and longer length of branch gaps. Length of lateral branches were longer under the warmer conditions. Thus, length of main shoot elongation and diameter of main shoot were greater under +2.0°C and +3.0°C treatments, but dry weight and T/R ratio remained almost the same. It was thought that the growth and the phenology of Chamaecyparis obtusa should change under the warmer conditions.