A 39-year-old man is in a stable condition in hospital after sustaining stab wounds to his back, chest and leg, according to Gwent Police.
A 47-year-old man has been arrested on suspicion of attempted murder following the attack on Friday in Llanarth Square, Pontymister, Caerphilly county.
The injured man is being treated at Cardiff's University Hospital of Wales.
Det Insp Michelle Chaplin said the force was not looking for anyone else in connection with the incident.
However, she appealed for any witnesses or individuals who may have any information about it to contact the force.