Magnetocaloric cooling is an alternative, high-efficiency cooling technology. In this paper, we present the design and fabrication of a micromachined magnetocaloric cooler and demonstrate its ability to work in a small magnetic field (< 1.2 T) with a cooling test. The cooler was built by fabricating Si microfluidic channels, and it was integrated with a Gd-5(Si2Ge2) magnetocaloric refrigeration element. The magnetic properties of the Gd-5(Si2Ge2) material were characterized to calculate the magnetic entropy change at different ambient temperatures. Three different methods to integrate the channel layer and the magnetocaloric element were evaluated to test sealing and cooling performance. The cooling tests were performed by providing a magnetic field using an electromagnet. A test jig was constructed between the poles of an electromagnet to maintain a steady temperature during the test. Cooling tests were performed on the magnetocaloric element at ambient temperatures ranging from 258 to 280 K using a magnetic field of 1.2 T. Experimental results showed a maximum temperature change of 7 K on the magnetocaloric element alone at an ambient temperature of 258 K. Cooling tests of the fully integrated coolers were also performed. A solution of anti-freeze fluid (propylene glycol) and water was used as the coolant. The temperature of the working fluid decreased by 4.6 and 9 K for the glass and Si intermediate layers, respectively, confirming that the thermal conductivity of the materials is also an important factor in cooler performance. Copyright (C) 2006 John Wiley & Sons, Ltd.