Silicon Avalanche Photodiodes (APDs) are used in NASA’s Global Ecosystem Dynamics Investigation (GEDI) that was launched in December 2018 and is currently measuring the Earth’s vegetation vertical structure from the International Space Station. The APDs were specially made for space lidar with a much lower hole-to-electron ionization coefficient ratio (k-factor ~0.008) than that of commercially available silicon APDs in order to reduce the APD excess noise. A silicon heater resistor was used under the APD chip to heat the device to 70°C to improve its quantum efficiency at the 1064-nm laser wavelength while maintaining a low dark current such that the overall signal to noise ratio is optimized. Special APD protection circuits were included to raise the overload damage threshold to prevent device damage from strong laser returns from specular surfaces, such as still water bodies, and space radiation events. The APD and a hybrid transimpedance amplifier circuit were hermetically sealed in a TO-8 type metal package with a sufficiently low leak rate to ensure a multi-year operation lifetime in space. The detector assemblies underwent a series of pre-launch tests per NASA Goddard Environmental Verification Standard for space qualification. The APDs have performed exactly as expected in space. A detailed description of the GEDI detector design, signal and test results are presented in this paper.