The conflict between Assam and Nagaland mostly relates to land encroachment. During the creation of Nagaland in 1963, an agreement was signed by the Naga People's Committee and the then Prime Minister, Jawaharlal Nehru. Some of the clauses in the agreement on land transfer to Nagaland remain unimplemented to date and have become the underlying cause of conflict between the two states.

Assam and Nagaland share a 434-kilometre border. In other words, about 66,000 hectares of land are disputed. This interstate border is divided into six sectors -- A, B, C, D, E and F. These sectors include Sivsagar, Golaghat, Jorhat and Karbi Anglong districts, all of which presently lie in Assam. Nagaland claims that sectors A, B, C and D belong to the Naga tribes and should not be a part of Assam.

During the colonial rule, the British government made these sectors a part of Assam for administrative convenience; these were supposed to be transferred to Nagaland after its creation. But till date, no such transfer has been made. The Assam government claims that since there has been no direction from the Centre in this regard, it shall not take steps to carve out the districts demanded by Nagaland.

This decades-old dispute has given rise to violent incidents over the years, leading to mass killings and displacement, and remains a constant cause of concern between the two states.

Two violent incidents in 1979 and 1985 resulted in over 100 fatalities. On 5 January 1979, armed men from Nagaland killed 54 Assamese people in a series of attacks on villages in Golaghat district. Over 23,500 people had to be accommodated in relief camps at the time. In June 1985, over 41 people in Assam were murdered, including 28 Assam police personnel at Merapani, also in Golaghat.

Several rounds of talks have been held between the two states to settle this dispute, but these have not led to any solution to date.

On 11 August 2014, Assamese people staged a protest outside a Central Reserve Police Force camp, demanding the release of two school students allegedly abducted by Naga insurgents. Following this, violence erupted as the All Adivasi National Liberation Army raided two villages along the Assam-Nagaland border – Ronsuyan and Chandalashung – beating up people and destroying property. This led to an exodus of over 10,000 people, who were moved to 14 relief camps in Uriamghat in Golaghat.

In the aftermath of this violence, the Assam government moved the Supreme Court. The dispute is being mediated by the Boundary Commission set up under the direction of the court.

In September 2020, after six years, Assam and Nagaland held a high-level meeting to address their border dispute. Assam proposed joint police patrols along the border, which Nagaland accepted in principle. However, tensions escalated in November when Assam accused Nagaland of establishing a police camp in the disputed Dissoi Valley Reserve Forest. While the situation has been controlled, the states are still awaiting a decision from the Supreme Court.

Meanwhile, a village along the Golaghat-Wokha border is caught in a tug-of-war between Assam and Nagaland as it still lacks basic amenities. The area, located within a Nagaland seed farm in Merapani, is claimed by both states—Assam considers it part of Golaghat district, while Nagaland claims it for Wokha. Although the villagers are voters in the Golaghat constituency, they reside within this disputed area, which has seen continuous neglect, including the last stretch of road connecting the two states. The CRPF is deployed to maintain law and order in the region.

A local official told LCW that Nagaland is willing to repair the road, but Assam's peace committee has denied permission. The official, who wished to remain anonymous, noted concerns that Nagaland's construction could lead to claims of ownership over the area.

In the Sivasagar district of eastern Assam, reports indicate that miscreants from Nagaland have illegally cleared about 1.5 bigha of land within the Geleky Reserve Forest. This was discovered during a joint patrol by Forest Department officials and Border Outpost personnel on 6 February 2024, who observed the recent tree felling on the eastern side of the Dorikhona River. On the contrary, Nagaland has expressed concern over the alleged encroachment by Assam on Nagaland’s Reserve Forest area in the nearby bordering Tuli region under Mokokchung district.

In April 2025, tension escalated further after the Nagaland government issued a directive to farmers in Merapani Bholaguri seed farm to cease seed farming activities and vacate the land. Over 1,000 farmers staged a massive protest against the directive.