A research entitled “Combination of Liquid Fertilizer of sea fish waste and Urea on mustard growth and yield (Brassica junce L.)” was carried out in the Green House, Faculty of Agriculture, Universitas Muhammadiah Yogyakarta from march up to may 2018. This research was conducted using environmental method and arranged in Completely Randomized Design with single factor. The treatments were consisting of 100% N-Urea (P1), 75% N-Urea + 25% N-Liquid fertilizer sea fish waste (P2), 50% N-Urea + 50% N- Liquid fertilizer sea fish waste (P3), 25% N-Urea + 75% N- Liquid fertilizer sea fish waste (P4), 100% N-POC Liquid fertilizer sea fish waste (P5). The results showed that combination of Liquid fertilizer sea fish waste and Urea govern on mustard growth and yield. Treatment (P3) 50% N-Urea + 50% N- Liquid fertilizer sea fish waste equal to 0,3 gram Urea + 4,4 ml gave the potential yield 38.777,5 tons/hectare