While there is extensive literature covering byproducts formed during various water treatment processes, there is limited research focusing on the generation of brominated disinfection byproducts (Br-DBPs) specifically during ozonation in the presence of bromide (Br−) and ammonium (NH4+). This study used Orbitrap mass spectrometry and a custom halogen extraction code to selectively pinpoint 109 Br-DBPs generated during the ozonation of Suwannee River natural organic matter (SRNOM) containing Br− and NH4+. The Br-DBPs are predominantly distributed ranging from m/z 190 to 320, with elemental compositions consisting of CHOBr and CHONBr. They mainly fell within the H/C (0.5–1.5) and O/C (0.2–1.0) zones, with 16 % being aromatic compounds. NH4+ suppressed Br-DBP formation in CHOBr1-2 subgroups but promoted it in CHONBr1-2 subgroups compared to Br−-containing SRNOM ozonation. Kendrick mass defect diagram revealed 64 identical Br-DBP formulas in the CHOBr1-2 subgroups in both systems, and among them, 13 brominated carboxylic acids were identified, whose formation was suppressed by the addition of NH4+. Moreover, bromonitrophenol and bromobenzonitrile were identified in CHONBr1-2 subgroups, and their formation pathways were proposed. Nitrogen-containing Br-DBPs, especially the aromatic nitrogen-containing ones, exhibited higher toxicity. Caution is necessary to minimize toxic Br-DBPs formation during Br− and NH4+-involved ozonation. This study offers insights into Br-DBP characterization, formation mechanisms and toxicity, guiding enhanced water treatment strategies.