Cecilio J. Morales, 59, manager of the economic and social development department of the Inter-American Development Bank here, died Saturday at Suburban Hospital after a heart attack. He lived in Bethesda.

He first joined the Bank here in 1967 as deputy program adviser and was its technical manager from 1968 to 1973, when he was appointed to the position he held at the time of his death.

Mr. Morales was born in Buenos Aires, Argentina. He held a degree in engineering from the University of Buenos Aires. He had served in the ministry of public health in Buenos Aires before coming to this country in 1952 as economic counselor of the Argentine delegation to the United Nations in New York.

He first came to Washington in 1958 as economic counselor of the embassy of Argentina, a position he held until 1960. During that period, in 1959-60, he also was director of the department of economic and social affairs of the Organization of American States. Other positions he held then included that of executive secretary of the Inter-American Economic and Social Council and of the Committee of 21, which had been created under the Alliance for Progress.

After serving two years as economic adviser to the president of Argentina, Mr. Morales entered the Inter-American Development Bank in 1962 and was its representative in Bolivia and later in Peru. He left the Bank for a year to serve with the technical affiliate of the Atlantic Community Development Group for Latin America in Lima, Peru.

Survivors include his wife, Ann K., of Bethesda; a son, Cecelio J. Jr., of Washington; another son, Cristian Francis, and a daughter, Maria Elena, both of Buenos Aires, and his mother, Jacinta M. de Morales of Buenos Aires.

The family suggests that expressions of sympathy be in the form of contributions to a charity of one's choice.