Authorities at the Chitwan National Park said the convicts, who were from a nearby Nawalparasi district, were also ordered to pay fine amounting from $550 -$1,100 each, Xinhua reported.
The one-horned rhino is an endangered species, protected in Chitwan, a place some 150 km from captial Kathmandu, along with two other national parks of Nepal.
Of the total 534 rhinos in Nepal, Chitwan National Park is home to 503. Bardiya National Park has 24 rhinos, while the remaining 7 are in Shukla Phanta National Park.
"Poaching has been a challenge for long against our conservation efforts. However, it is positive that poaching of rhino has significantly reduced in the last decade," Tikaram Poudel, assistant conservation officer of Chitwan National Park.
In 2003, poachers gunned down 37 rhinos in a year, whereas in 2012, only one rhino was killed.
He said the numbers of check posting the park have been increased to around 50, while over 1,000 government employees including security personnel are part of the park's management team.
Rhinos are killed by poachers for their horns, which are used for various purposes including the production of traditional medicines.