Cabbage, a widely cultivated cruciferous vegetable, generates substantial waste material during its harvest and processing. This study was conducted to analyse the effectiveness of three decomposer types and their concentration to break down cabbage waste compost on the cultivation of lettuce (Lactuca sativa L.). The research employed randomized complete block design with two factors and three replications. The first factor was the cabbage waste compost amount: 20 g, 30 g, and 40 g per plant. The second factor was type of compost decomposers: without decomposers, EM4, Thiobacillus sp., and indigenous microorganism. Variables observed included leaf length, number of leafs, leaf fresh weight, leaf dry weight, root fresh weight, root dry weight, and root length. Data were analysed using analysis of variance and means were separated using Duncan’s multiple range test. There was no interaction between the decomposer and the amount of cabbage waste compost on all parameters. The type of cabbage waste compost decomposer had a very significant effect on the number of leaves and root length. The amount of cabbage waste compost did not significantly affect all parameters. Indigenous microorganism (IMO) decomposer resulted in the number of leaf 14.36 and leaf length of 5.79 cm.