Police attended the scene in La Chaux-de-Fonds after they were alerted at around 9.30pm on Sunday night.
A 62 year-old woman was found dead in an apartment, presenting knife wounds, Neuchâtel police said in a statement on Monday.
The woman's 36-year-old husband was seriously wounded but had managed to call on neighbours for help. He was flown by helicopter to hospital in Bern.
Initial investigations led police to identify the alleged perpetrators, including the 31-year-old son of the female victim, who was arrested just 40 minutes later. He did not resist arrest.
Another suspect turned himself in to police later that night.