Mangrove forests have soil characteristics that are muddy, wet, and rich in organic matter and if organic and inorganic fertilization activities are carried out, it is expected to affect both the soil and plants. This study aims to determine whether there is an effect on the growth of Rhizophora apiculata seedlings fed with NPK fertilizer, chicken manure, cow manure, quail manure or not. This research was conducted from October 2020 to May 2021 in the Mangrove Forest of Lubuk Kertang Village, Pangkalan Brandan Barat, North Sumatra. This study used a non-factorial completely randomized design consisting of 5 treatments and 4 replications. Variables observed were increase in seedling height, increase in seedling diameter, increase in number of leaves, temperature, plant wet weight, plant dry weight, leaf area. The results showed that the treatment with P3 (cow manure 200 g/plant) gave the best effect and results when compared to P0, P1, P2, and P4 because P3 fertilizer had the largest dose.