Nha Trang came in third, followed by Hanoi and Phu Quoc, based on Agoda's booking data between January and June.
Hoi An and Ho Chi Minh City rounded out the top 5, offering a mix of cultural heritage and urban exploration.
In the first five months of this year, Da Nang served 4.6 million visitors, up 18% year-on-year, including over 2 million foreign arrivals.
The number of foreign visitors to Vietnam in the first half of this year reached 10.7 million, up 20.7% year-on-year but still lower than Thailand's 16.6 million.
Mainland China remained the top source market during the January-June period, with 2.72 million arrivals, a 44% year-on-year increase, followed by South Korea (2.2 million), Taiwan (629,000), the U.S. (449,000), and Japan (393,000), according to the General Statistics Office.
Agoda said South Korean travelers show a clear preference for coastal and island destinations.
Nha Trang tops the list of Vietnamese destinations searched by Korean travelers, followed closely by Da Nang and Phu Quoc Island, which are favored for their beaches and water activities.