A 19-year-old Kensington man has been indicted by a federal grand jury on a charge that he violated a federal fair housing law by intimidating a black family in his neighborhood.

The one-count indictment against John J. Moscato of South Cushing Drive was handed down in U.S. District Court in Baltimore Tuesday. If convicted, Moscato could receive one year in prison and a $1,000 fine, according to Justice Department officials.

The indictment follows a series of racially motivated incidents against a black family, the Hymans, who moved to Kensington at the end of 1980. Alexander E. Hyman said the problems began a few months after he, his wife and five children moved to the middle-class neighborhood.

"It was an eerie thing to go through," said Hyman, 45, the director of the high school equivalency program for the D.C. school system. "It was like something out of the '40s or '50s."

Moscato lives across the street from Hyman. Efforts to reach Moscato for comment were unsuccessful.

The two-page indictment accuses Moscato of pasting swastika symbols on Hyman's car on Dec. 15, 1980. In late February, the indictment charges, Moscato mailed a letter containing swastika symbols to the Hyman household.

The letter included the phrases "The future belongs to us" and "The Holocaust--six million lies," according to the indictment. Federal officials also charge that in April 1981, Moscato tried to intimidate the Hymans with a note that read, "NIGGERS get out of here."

The indictment comes at a time when reports of racially motivated incidents in the county have grown significantly since 1980, prompting county officials to conduct programs on "hate-violence" incidents for such groups as students and businessmen.

Joan Weiss, an employe of the county's Human Relations Commission, said 98 incidents of a racial or religious origin were recorded in the county last year, an increase from the 25 reported in 1980. Weiss added that the number of incidents reported so far in 1982 is ahead of last year's figures.

Hyman said yesterday that some good has resulted from the harassment of his family. "One woman cried for me when these things started," he said. "Some others sent cakes and cookies and said that they were sorry these things were happening.

"I've got some of the best neighbors in the world."