Prey Veng province is 4,883 square kilometres big.

It's located in the South of the country and is bordering to the North with Kampong Cham, to the West with Kandal, to the East with Svay Rieng and to the South with Vietnam. The province consists of the typical plain wet area for Cambodia, covering rice fields and other agricultural plantations (rubber plantations in former times). The province also features two of the biggest rivers of the country the Tonle Bassac and the mighty Mekong.

The province is bordered by those of Kampong Cham to the northwest, Tbong Khmum to the northeast, Kandal to the west, and Svay Rieng to the east and by Vietnam to the south. It is crossed by two major rivers of the country, namely the Mekong and Tonle Bassac.

The total land area of the province is 4,883 km², which equals 2.7% of the total land area of Cambodia (181,035 km²). This consists of 445.18 km² or 9.12% of human settlements, 3,100 km² or 63.49% of agricultural land use, 194.61 km² or 3.99% of forested area, 1,082.86 km² or 22.18% of public land, infrastructure and water bodies. The remaining 60.35 km² or 1.24% are unused areas.