The species inhabits tropical rainforest and montane moss forest, and occasionally occurs at forest margins and in secondary forest (Nowak 1999). Sumatran Rhinos occur mainly in hilly areas nearby water sources, and exhibits seasonal movements, moving uphill in times of lowland flooding (van Strien 1975). This shy species is dependent on salt licks, and occurs mostly in primary forest in protected areas, but wandering into secondary forests outside protected areas, especially in the dry season in search of water (van Strien 1975).

Males are primarily solitary, but can have overlapping territories with females, which are commonly found with offspring (Nowak 1999). The home range size of females is probably no more than 500 ha, while males wonder over larger areas, with likely limited dispersal distance. The species is generally solitary, except for mating pairs and mothers with young (Nowak 1999). Its life history characteristics are not well known, with longevity estimated at about 35–40 years, gestation length of approximately 15-16 months. Captive females have copulated as early as six years of age, and males at eight years of age (Miller et al. 2015; IRF website 2018, www.rhinos.org). Females may develop reproductive pathologies if they do not become pregnant (Roth pers. comm). Because they are induced ovulators (Roth et al. 2001) timing of females meeting males is critical; females are most likely to become pregnant when an ovarian follicle is approximately 20 mm in size prior to copulation.

Home ranges are up to 5,000 ha for males, 1,000–1,500 ha for females. Daily movements between feeding sites and wallows are probably only a few kilometres per day. Longer treks are made when males and females go to saltlicks (5-10 km) and by males exploring their large ranges. Dispersal appears to be mainly by sub-adult animals (4-7 years) old. In this period they may be found rather far from the home grounds. Adults are very traditional in the use of their ranges and will not move away unless severely disturbed. Water is never very far away in the habitats occupied by the Sumatran rhino.

The Sumatran Rhinoceros once occurred from the foothills of the Himalayas in Bhutan and north-eastern India, through southern China (Yunnan), Myanmar, Thailand, Cambodia, Lao PDR, Viet Nam and the Malay Peninsula, and onto the islands of Sumatra and Borneo in Indonesia (Foose et al. 1997, Grubb 2005). The species' precise historical range is indeterminate, as early accounts failed to distinguish rhinos to specific level, due to partial sympatry with the other two Asian rhino species (Rhinoceros sondaicus and Dicerorhinus sumatrensis).

The subspecies Dicerorhinus sumatrensis lasiotis formerly occurred in India, Bhutan, Bangladesh, and Myanmar (Nowak 1999). The subspecies is extinct in the three former countries, but there is a possibility that a tiny remnant population remains in northern Myanmar.

The subspecies Dicerorhinus sumatrensis harrissoni formerly occurred throughout the island of Borneo. The subspecies now is considered extinct in the wild in Sabah (Malaysian Borneo). A handful of individuals may still survive in east Kalimantan (Indonesian Borneo) (Kurniawan, pers. comm.).

Dicerorhinus sumatrensis sumatrensis formerly occurred in Thailand, Peninsular Malaysia, and Sumatra (Indonesia). Presently, the subspecies primarily occurs in three protected areas in Sumatra (Miller et al. 2015); there may be a handful of stragglers living outside protected areas, particularly in Aceh Province. The continued existence of a rhino population in Bukit Barisan Selatan National Park is in question due to unprecedented disturbance and illegal activities in the park.

The species occurs from sea level and up to 2,500 m asl.

The species has been included on CITES Appendix I since 1975, and legally protected in all range states. Rhino Protection Units (RPUs) have been a force majeur in fighting poaching in Sumatra. Many organizations are involved with these units, which work under a Memorandum of Understanding with the Government of Indonesia's Ministry of Environment and Forestry. The expansion and reinforcement of anti-poaching programs, as well as expanding the current captive breeding program, are the top priorities if this species is to survive.

A standardized method for rhino monitoring has been developed and launched (Tim Monitoring Badak Sumatra 2014). However, it has only been partially implemented and in few areas. The low number apparently poses a big challenge in obtaining an adequate sample that will result in reliable population estimates. Meanwhile, there has also been a concern about introducing disturbance if an intensive survey is conducted in sensitive areas. Because of this, to-date no robust population data are available. The current survey is directed to focus on identifying rhino that are considered "doomed" and to be rescued as recommended by the PVA analysis (Miller et al. 2015) and endorsed under the Government of Indonesia's Emergency Action Plan.

There are ongoing efforts to further develop capacity for managed breeding in Indonesia. There have been recent advances in captive breeding techniques for this species, including successful births at the Cincinnati Zoo & Botanical Garden in 2001, 2004, and 2006 and at the Sumatran Rhino Sanctuary in Sumatra in 2012 and 2016. All the animals from Cincinnati Zoo & Botanical Garden (United States) have now been transferred to the Sumatran Rhino Sanctuary. The size of the facility will be doubled by the end of 2019 so that it can hold more animals. The Government of Indonesia has endorsed further rhino rescues to speed up conservation breeding. In late 2018, a collaborative project led by the Ministry of Environment and Forestry, involving the IUCN SSC, the International Rhino Foundation, WWF, National Geographic, and Global Wildlife Conservation and Yayasan Badak Indonesia, WWF-Indonesia, and Forum Konservasi Leuser in-country, was launched to speed up the conservation breeding of the species by expanding the Way Kambas Sumatran Rhino Sanctuary and to develop new captive breeding centres in Leuser and in Kalimantan.

The Government of Indonesia published its "Strategy and Action Plan for the Conservation of Rhinos in Indonesia" covering the time period of 2007 to 2017. A further conservation strategy for the Indonesian Sumatran rhino populations was developed in a series of workshops in 2014 and 2015. The Government of Indonesia launched an Emergency Action Plan in early 2019. 

In Sabah, Malaysia, the Borneo Rhino Alliance focused on collecting oocytes from an older female, in the hopes of creating an embryo using semen from Sumatran Rhino Sanctuary males. To ease collaboration between the countries, the Government of Malaysia has the State of Sabah to act on behalf of the Government of Malaysia. The Governments of Indonesia and Malaysia have, in principle, agreed to this exchange but for various reasons no exchanges have occurred. No successful oocyte collection has occurred with this female to-date.

There is a need for further surveys in Myanmar and in Kalimantan to determine the location of any remaining animals.