"Blocking Human Rights Watch from holding a news conference in the UAE sadly underscores the increasing threat to freedom of expression in the country," said Sarah Leah Whitson, HRW's chief for the Middle East and North Africa.
"If the UAE wants to call itself a global media centre, it needs to show that it respects freedom of speech and the open expression of critical ideas, not shut down media events," said Whitson.
But hotel staff informed the UAE early in the morning that the reservation had been cancelled, saying the watchdog had failed to obtain a special government permit to hold the conference, said HRW.
In the report seen by AFP, the watchdog accuses the UAE of having "stifled free expression, and subjected dissidents to manifestly unfair trials marred by credible allegations of torture" last year.
More From This Section
On Tuesday, a top UAE court jailed a group of 30 Emiratis and Egyptians to terms ranging from three months to five years for forming a Muslim Brotherhood cell.
The 10 Emirati citizens were among 69 nationals jailed in July for up to 15 years on charges of plotting to overthrow the government.
"The UAE's repressive laws and dysfunctional justice system belie the government's efforts to present the country as moderate and progressive," said Whitson.
The Gulf state has not seen any of the widespread pro-reform protests that have swept other Arab states, but authorities have boosted a crackdown on dissent and calls for democratic reform.
HRW also accused the UAE of failing to improve the rights of migrant workers.
In May, the UAE slapped deportation orders on 43 migrants who joined a rare strike by workers at the Arabtec construction giant to demand better pay and conditions.
Rights groups have repeatedly criticised the UAE and other Gulf countries for their treatment of millions of foreign workers, mostly Asians.