Micro-power sources that are comparable to or smaller than the size of the micro-devices needing power are needed for many applications. This paper introduces an integrated millimeter scale power source based on a micro-silicon fuel cell and a MEMS hydrogen generator, with passive control. The integrated devices are fabricated from silicon wafers using conventional MEMS fabrication processes. In this design, the hydrolysis reaction of calcium hydride and water is used to generate hydrogen, and the hydrogen generation rate is controlled by a microfluidic self-regulating mechanism, which can control the hydrolysis reaction based on the load. Design, fabrication, and testing results of a prototype system are described. One of the devices can produce 90μW for 6h with a maximum power of 0.17mW, and another one can produce 30μW for 26h with a total energy density of 100WhL−1.