Reliability characteristics of thermoelectric module (TEM) depends on case-by-case application and availability. A military soldier’s portable thermoelectric generator (TEG) mainly consists of thermoelectric modules, heating parts, cooling parts, and power circuit. Thermoelectric module is a key factor to determine the mechanical and electrical durability of a military portable TEG. From the life cycle environmental history of the TEM as an application of soldier’s portable power sources, the main natural and induced environmental stresses were categorized into high temperature, low temperature, humidity, vibration and shock. According to MIL-STD-810F, reliability tests of TEM were successfully carried out under the environmental conditions simulated deployment of a military solider use. In this study, Bi-Te thermoelectric module was used to evaluate its environmental and mechanical reliability under the military environmental conditions. The bismuth-telluride (Bi-Te) TEM after environmental tests exhibits a slight decrease of maximum output power about 3 ~ 6%. A humid atmosphere is more harmful to the electrical performance of TEM as an application of portable power generator, and the TEM should be encapsulated by metal housing with an inert or vacuum atmosphere or sealing its outer perimeter to prohibit it from water contact. The Bi-Te TEM after environmental tests exhibits no visual evidence of mechanical damage. The Bi-Te TEM after mechanical tests (vibration and shock) exhibits no degradation of maximum output power, and no visual evidence of mechanical damage, such as cracking or deformation. This reliability test data of TEM can provide good design factors in designing a military portable thermoelectric generator.