Two years after the New York Blood Center set off a storm of protest from animal welfare advocates by withdrawing support for a colony of chimpanzees used for biomedical research, the organization has joined with the Humane Society of the United States to guarantee their future care, pledging $6 million.

In a joint announcement on Tuesday, the two groups said the blood center would donate the money to the Humane Society, which will assume responsibility for the lifetime care of the chimps. In captivity, chimps can live 50 to 60 years.

In the statement, Dr. Christopher D. Hillyer, head of the blood center, said he was “pleased that we have found a capable organization to take care of the chimpanzees for their lifetime.” He said the agreement would allow the blood center to concentrate on ensuring the blood supply.

The donation amounts to roughly half the estimated cost of caring for the animals on their island sanctuary in Liberia, said Wayne Pacelle, the head of the Humane Society of the United States. Mr. Pacelle said he was delighted that the two groups had “found a path forward.”