This research aims to examine the effect of several seaweed extract concentrations on the growth of cassava stem cuttings and determine the most effective concentration of seaweed extract for the growth of cassava stem cuttings. This research was conducted using an experimental method using a single factor experiment, with Completely Randomized Design (CRD), consisting of 5 treatments namely adding 2000 ppm Seaweed Extract, 3000 ppm Seaweed Extract, 4000 ppm Seaweed Extract, 300 mg/l Rootone-F and water. Parameters observed included shoot number, shoot length, leaf number, leaf area, root length, root number, root fresh weight, root dry weight, root fresh weight, root dry weight, shoot fresh weight and shoot dry weight. The results showed an addition of 2000 ppm seaweed extract, 3000 ppm seaweed extract, 4000 ppm seaweed extract, 300 mg/l Rootone-F and water on the parameters of the number of shoots, shoot length, leaf number, leaf area, root length, number root, fresh root weight, root dry weight, fresh shoot weight showed no significant difference. The mean results of analysis of variance in the addition of 3000 ppm seaweed extract were higher in growth in parameters of number of shoots, number of leaves, leaf area, number of roots and root dry weight. While the parameters of shoot length, root length, root fresh weight and the highest fresh shoot weight were shown in the addition of 300 mg/l Rootone-F.