Magnetic-activated biocarbon (MAB) composite has been prepared from red algae and applied to remove methylene blue (MB) and Remazol brilliant yellow FG (RBY) dyes from water. Biocarbon prepared from red algae, following synthesized of magnetic biocarbon composites with nickel chloride hexahydrate (NiCl2.6H2O) and activated using various concentrations of KOH. Each MAB composite’s adsorption efficiency (%E) for adsorption was examined. The MAB composite with the highest adsorption efficiency was used for the adsorption study with various contact times, pH, adsorbent masses/dosages, and initial concentrations of dyes. The MAB composite was characterized by Fourier Transform InfraRed (FTIR), Scanning Electron Microscopes (SEM), X-ray diffraction (XRD), and Particle Size Analyzer (PSA). The results showed that MAB composite optimal results in red algae: KOH ratio of 1: 0.5 (RA(Ni)0.5). The adsorption results showed that the optimum adsorption conditions for MB and RBY dyes occurred at pH 10 and 4, an adsorption time of 80 and 60 minutes, adsorbent dosages of 0.1 and 0.2 g, and adsorbate concentration of 35 mg/L with absorption efficiency (%E) of 95.99 and 89.94%, and adsorption capacity of 16.799 and 7.869 mg/L, respectively. The isotherm model for MB and RBY dye adsorption is the Freundlich isotherm (R2 = 0.9914), and the Langmuir isotherm (R2= 0.995), respectively. Regeneration test revealed that, RA(Ni)0.5 composite is more efficient in adsorbing cationic dyes (MB – 83.02%) compared to anionic dyes (RBY – 67.08%) after 15 repetitions. RA(Ni)0.5 composite is proven to have the potential as an adsorbent for the adsorption of MB and RBY dyes from water.