Trashigang Dzongkhag shares its border with Mongar Dzongkhag in the west, Samdrup Jongkhar and Pemagatshel Dzongkhag in the South, TrashiYangtse Dzongkhag in the north and Indian state of Arunachal Pradesh in the east. Trashigang is 551 km away from Thimphu, the capital city and is one of the largest Dzongkhags in the Kingdom. The Dangmechu, one of the largest rivers in the country passes through the Dzongkhag. The altitude elevation ranges from 600 m to over 4500 m above sea level. The climate is mainly temperate with an annual rainfall between 1000 mm and 2000 mm. The lowest human settlement is found at an altitude of 550 m above sea level at Deno of Lumang Gewog and the highest at Merak at an altitude of 4600 m above sea level.
Trashigang Dzongkhag has a total area of 2204.5 square kilometers. It has a total of 8,610 households with population of 71,768. The density of population is 33 per sq.km. The forest cover accounts for 77.87 percent of the total. The Dzongkhag has arable land of 3.64 percent of its total area.
The Dzongkhag Administration Headquarters and the main town are located at Mithidrang, which falls under Samkhar Gewog. The Dzong is used as the Dzongkhag Headquarters and also as the seat of Dzongkhag Rabdhey.
Trashigang Dzongkhag is administratively divided into three Dungkhags, 15 Gewogs and 79 Chiwogs including a Thromde. All the gewogs, except Sakteng are connected with motorable roads.