Construction will start within two weeks on a 400-room, $25 million Marriott hotel at Tysons Corner - the third area hotel project involving the Bethesda firm announced in the past 11 months.

Marriott will manage the 15-story hotel for a partnership of Washington investors called Hollinswood Associates. The management contract covers 25 years and has options for several extensions, according to a spokesman for the investor group, Washington lawyer Donald Brown.

Situated on a five-acre site at the northeast corner of Leesburg Pike and Mimosa Drive, adjacent to an entrance to Tysons Corner Center, the new hotel is scheduled to open early in 1981.

A Marriott-owned Roy Rogers restaurant adjoining the site will remain in business as an alternative facility to the hotel's restaurants and a 600-car, multilevel garage also will be constructed.

Brown said the investors include Benjamin Jacobs and Joseph Gildenhorn, his law partners; James Clark, president of George Hyman Construction Co.; real estate businessman George Kettle and Manuel Fernandez, head of the Channel Inn Motel in Washington.

Under the name of JBG Associates, Brown and his law partners have developed an extensive real estate developing, ownership and managing business, with some $175 million of area projects planned or in progress. Each project includes different outside investors.

The Tysons Corner Marriott will include a number of convention-type facilities, including a 4,500-square-foot ballroom; a possible division of various spaces into a dozen meeting rooms; a 200-seat restaurant and 150-seat disco and cocktail lounge and an indoor pool with exercise facilities.

According to Brown, Marriott market surveys recently pinpointed the Tysons area as one of the five markets worldwide without a Marriott hotel that showed the most promise of future business growth.

Long-term financing will be provided by Connecticut General Life Insurance Co., and mortgage brokerage was provided through the Rouse Co.

Two Marriott hotels in downtown Washington - at 22nd and M Streets NW and along Pennsylvania Avenue - were announced last year and Marriott opened its first Maryland hotel in Bethesda last month.

In an unrelated development, Marriott executives last night held a reception at the $1 billion firm's new headquarters near Montgomery Mall, celebrating dedication of the complex, to be named the J. Willard and Alice S. Marriott Building.