Bach Ma National Park is situated in the central Annamite mountains. The national park lies on a high mountain ridge that runs west-east from the Laotian border to the East Sea at the Hai Van pass. This ridge interrupts the coastal plain of Vietnam, and, therefore, forms a biogeographical boundary between the faunas and floras of northern and southern Vietnam. This ridge also affects the local climate at the national park, which is probably the wettest place in Vietnam: the mean annual rainfall at the summit of Mount Bach Ma is 7,977 mm.
The geology of the national park is dominated by granite, with some overlying areas of sandstone, schist and gneiss. The topography is generally steep and rugged, formed by heavy dissection of the substrate by surface water. The national park is dominated by a west-east ridge, with several peaks above 1,000 m, the highest of which is Mount Bach Ma at 1,448 m. The lower slopes and hills are less steep, and are bordered by a narrow alluvial plain.
There are many springs on the lower slopes and foothills of the national park. Generally, the north of national park is drained by the Truoi river, which flows into the coastal lagoons south of Hue city. The south of the national park is drained by tributaries of the Ta Trach river, which flows westwards.