They had previously denied charges of negligence, manslaughter, and obstruction of justice.
The pair appeared today in the Supreme Court for the start of an expected two week trial, but their lawyer entered guilty pleas.
One defendant, Luse Emo Tauvale, has admitted to three charges of obstruction of justice and two of negligence and manslaughter, while Leutogi Te'o has pleaded guilty to one charge of manslaughter.
Other prosecution charges against the nurses have been withdrawn.