North Sumatra is one of the provinces that has a large fishery potential. The total catch of in North Sumatra reached 380,349 tons in 2016. This research to determine the growth pattern of Euthynnus sp. that caught in the waters of Nias Island, North Sumatra. Sampling was carried out in July 2020. The study was conducted by following fishing operations on purse seine vessels start from Sibolga City. Sample of 59 fish were taken randomly during the operation of the fishing gear in one trip. Length of fish was measured using a ruler (nearest: 1 mm) and weight of fish was measured using a digital scale (nearest: 1 g). The result of this research was the total length of the fish about 350–530 mm. There were 7 classes Length Distribution of fish that caught in July 2020. The highest frequency of total length was 401-427 mm. The growth pattern of Euthynnus sp. was positive allometric growth (b > 3). The Formula for Length-Weight Relationships is W = 0.06L3.2611 (r = 0.97). The length-weight relationship can describe the condition of fish population growth and the symptoms of fishing in nature. This is necessary to support the management of fishery resources.