A new technique was developed to make magnetic observations of weakly magnetized materials under hydrostatic pressure up to 12 kilobars in a wide temperature range from liquid helium temperature up to 200°C. We have designed a special type of nonmagnetic pressure vessel in which the materials to be measured were pressurized. For measuring magnetization, the above pressure vessel was connected to a torsion pendulum and its deflection in a magnetic field was measured. For measuring the anisotropy of ferromagnetic crystals, the vessel was connected to an air‐jet supported magnetometer having an unbonded strain gauge detector and its torque moment in a uniform magnetic field was determined.