The once-struggling park said profit more than doubled to HK$242 million (US$31.2 million) in the last fiscal year that ended September, compared with US$14.06 million in the same period of 2012, with a record attendance of 7.4 million visitors.
It said the increase in attendance was largely due to more mainland tourists visiting.
"Asia is experiencing strong economic growth. Disposable income around Asia is improving and that has stimulated the tourism industry within Asia," Hong Kong Disneyland managing director Andrew Kam told a news conference.
"I don't have a crystal ball... but as long as disposable income keeps increasing, the demand for outbound travel certainly will continue" to grow in mainland China and the rest of the region, he said.
Kam said the theme park's two existing hotels had an overall occupancy rate of more than 90 percent for the past three years.
He said the new hotel would add 750 rooms to the existing capacity of 1,000 and would require a new investment of HK$4.26 billion, partly funded by the Hong Kong government, the park's largest shareholder.
Hong Kong Disneyland is 52 percent-owned by the city's government.
The park reported its first-ever annual profit since its 2005 opening in the 2012 fiscal year, totaling US$14.06 million, while attendance stood at 6.7 million visitors.
The new hotel would open as early as 2017, he said.