<p>The effects of Ni content and brazing treatment on the microstructure and mechanical properties of Al-1.7Mn-xNi (<i>x</i> = 0, 0.5, 1, 1.5, 2.5) aluminum alloy were investigated by optical microscope (OM), scanning electron microscope (SEM), X-ray diffraction (XRD), transmission electron microscope (TEM), and tensile test. The results show that the microstructures of five alloys are mainly composed of primary <i>α</i>-Al grains and eutectic structure. As the Ni content increases from 0 to 2.5 wt.%, the amount of eutectic structure significantly increases, and the type of eutectic second phase changes from Al₆Mn to Al₆Mn/Al₉(Ni,Mn,Fe)₂, finally to Al₉(Ni,Mn,Fe)₂. After brazing at 605&#xa0;°C for 20&#xa0;min, eutectic second phases are spheroidized and coarsened, new Mn-rich phases are formed adjacent to the Al₉(Ni,Mn,Fe)₂ phases, meanwhile, large numbers of Al-Mn-Ni dispersoids precipitate from the matrix. Tensile test shows that the ultimate and yield strength increase with the increase of Ni content, while the elongation decreases. The increase of the amount of eutectic structure is the main reason for the increase of strength of as-cast sample. Compared to the as-cast sample, the strength of as-brazed sample decreases and elongation increases, which is mainly due to the spheroidization and coarsening of eutectic structure and the precipitation of solid solution atoms.</p>