It said 84 percent of the nearly 1,980,510 people have been internally displaced for over a year.
The report also said 946,044 internally displaced people had returned to their homes and 280,623 refugees and asylum seekers, mainly from Somalia and Ethiopia, are in the country.
Additionally, the report said the "UNHCR remains deeply concerned by the significant impact the escalating hostilities are having on the protection of civilians and on the increase of newly displaced persons."
The conflict in Yemen has raged since 2014, when Houthi militias and their allies overran much of the country, including the capital Sanaa.
A coalition led by Saudi Arabia launched a massive air campaign a year later aimed at reversing Houthi gains and returning President Abdrabbuh Mansur Hadi to power.
The war has killed at least 10,000 people, destroyed Yemen's economy, caused a cholera epidemic and forced millions from their homes amid a looming famine.
ReliefWeb is the leading humanitarian information source on global crises and disasters. It is a specialized digital service of the UN Office for the Coordination of Humanitarian Affairs (OCHA).