Night break effect is widely used in chrysanthemum production by applying incandescent (INC) lamps to inhibit flowering of chrysanthemum in order to obtain longer shoots. To save energy, LED lamps had been developed as a new light source and used in agriculture. Since there is limited research on chrysanthemums grown in LED light culture, we studied the night break effect by using several different wavelengths of LED lamps. Red (R) light from LED-630 and LED-660 had perfect inhibition on floral bud differentiation in 'Jimba,' but could not inhibit that in 'Iwa no hakusen' chrysanthemums. The far-red (FR) light of LED-735 had no effect on the inhibition of floral bud differentiation in 'Jimba,' but it was delayed in 'Iwa no hakusen.' Treatments of LED-690 and INC lamps inhibited floral bud differentiation in 'Jimba' and strongly delayed that in 'Iwa no hakusen.' Treatments of a combination of R light of LED-660 and FR light of LED-735 inhibited floral bud differentiation in both the cultivars.