The ferromagnetism in Cr-based monolayers is of current interest (2019 Nat. Nanotechnol. 14 408), however, the Curie temperature is low. How can we enhance the thermal stability of ferromagnetism? Motivated by the recent synthesis of the layered conductive magnet CrCl2(pyrazine)2 (2018 Nat. Chem. 10 1056), we perform first-principles calculations and Monte Carlo simulations to demonstrate that the exfoliated 2D CrCl2(pyrazine)2 monolayer is stable dynamically and thermally, and it is a ferromagnetic half-metal with a sizeable band gap of 2.8 eV in the semiconducting channel, and the strong in-plane Cr-Cr interaction results in a large magnetic anisotropy energy. Moreover, the sheet exhibits a high Curie temperature of 350 K due to the enhanced magnetic exchange interaction resulting from the aromatic property of pyrazine. All of these intriguing features endow 2D CrCl2(pyrazine)2 sheet with good potentials for applications in nanoscale spintronics devices.