Nettie Ottenberg, 95, a former social worker and a persuasive and tireless advocate in behalf of such causes as child day care and voting rights, died May 11 at her home in Washington. She had pneumonia.

Mrs. Ottenberg, who was born near Odessa, Russia, grew up in New York City. There she became interested in the welfare of the poor--in her early days, she was no stranger to poverty herself. She was a member of the first class to graduate from the School of Philanthropy, which later became part of Columbia University. She put herself through school by earning $5 a week as a secretary.

"It was the day of Jane Addams and Hull House," she said in an interview with The Washington Post in 1977. "We learned first hand how to administer charity. And we learned the first rule, that charity today is justice tomorrow."

At 19, she became a probation officer in the juvenile court in Philadelphia. "I never committed one boy to an institution," she used to say.

During these years, Mrs. Ottenberg also was a suffragist, working to secure the vote for women. That came to pass with the ratification of the 20th amendment of the U.S. Constitution in 1920.

But it was many more years before Mrs. Ottenberg herself could vote in presidential elections. For in 1912, she married Louis Ottenberg, son of the founder of the Ottenberg Bakery, and moved to Washington. Residents of this city were not permitted to vote in presidential elections until 1964.

The projects on which Mrs. Ottenberg worked over the years include reform of women's prisons, child labor and juvenile court systems. She helped write the District's juvenile court law.

In later life, she was best known, perhaps, for her efforts to provide day care for the children of working mothers. In 1962, she persuaded Sen. Robert Byrd (D-W.Va.) of the need for federal funding for day care centers. The sum appropriated was $50,000 for use in the District of Columbia.

She was a founder of the National Child Day Care Association and later successfully lobbied for a $1.5 million appropriation for a model day care program in the city. An aspect of this was health screening for children. At the time of her death, Mrs. Ottenberg was still working for enactment of a program that would give a tax exemption to landlords who provide day care for the children of their tenants.

"I don't have time to think about old age," she used to say. "I try to listen to the problems of today."

Mrs. Ottenberg's husband died in 1960. Survivors include three children, Mrs. Jerome H. Greenhill of North Miami Beach, Fla., Miriam Ottenberg of Washington, and Louis Jr. of Bethesda; three grandchildren, and two great-grandchildren.