The need for tomatoes on the market has increased, but not accompanied by high yields which resulted in the need for tomatoes on the market is not met. One of these problems must be resolved, one of which is by applying fertilizers according to the needs of the plant. Fertilizing at this time does not have to use chemical fertilizers but must be brave to utilize what is around us and contain fertilizer ingredients. The purpose of this study was to determine the right dosage in the application of leaf fertilizer from seaweed extracts to tomato plant growth and yield. The research was conducted on the experimental field using soil media in polybags and at the Laboratory of the Faculty of Agriculture, Muhammadiyah University, Yogyakarta. This study used an experimental method with a single factor treatment arranged in a Complete Random Design (CRD) consisting of 5 treatments, namely: R0: without seaweed extract, R1: 1000 ppm seaweed extract, R2: 2000 ppm seaweed extract, R3: 3000 ppm seaweed extract, and R4: 4000 ppm seaweed extract. The treatment of seaweed extract gave significantly different results on the diameter and weight of tomatoes. The highest yield was obtained from the treatment of 4000 ppm seaweed extract concentration of 2.03 tons / ha.