In this paper, the physical properties such as structural, electronic, and magnetic of vanadium diselenide, chromium diselenide, molybdenum diselenide and tungsten diselenide monolayers were studied. The calculations were performed in the hexagonal structure (1H) and using the density functional theory. The computational calculation shows that the exfoliation energies of four monolayers are 18.92 meV/Å2, 19.83 meV/Å2, 22.42 meV/Å2, and 33.85 meV/Å2, respectively. While the formation energies values per atom were −2.88 eV, −2.47 eV, −3.31 eV, and −.398 eV, respectively. The monolayers are thermodynamically stable because the formation energies are negatives. Finally, the band structure study reveals that vanadium diselenide monolayer have a half-metallic ferromagnetic behavior, while the chromium diselenide, molybdenum diselenide and tungsten diselenide monolayers present a direct semiconductor character. Due to these properties the monolayers have potential application in micro, nano electronics, and spintronic devices.