<p>Mustard greens (<i>Brassica juncea</i> L.) is one of the horticultural crops of vegeTable species that are utilized in young leaves. Utilization of seaweed as biofertilizer can be an alternative solution to environmental problems caused by mineral fertilizers because they are safe for soil and plant microbes. The research aimed to determine the effect of extract of seaweeds growing Central Sulawesi on growth and yield of mustard greens. This study consisted of six treatments: P₀ = control, P₁ = NPK fertilizer, P₂ = seaweed extract <i>Caulerpa</i> sp., P₃ = seaweed extract <i>Sargassum</i> sp., P₄ = seaweed extract <i>Kappaphycus alvarezii</i>, P₅ = seaweed extract <i>Ulva</i> sp., Plant height, number of leaves, leaf area, fresh weight of plant, dry weight of plant, and chlorophyll content were measured during the growing period and at harvest. The results showed that the seaweed extracts significantly affected on growth and yield of mustard greens plants. The most effective seaweed extracts for mustard greens plants was from <i>Ulva</i> sp. which produced average leave fresh weight 772.79 g and 10.40 numbers of leaves.</p>