Officers were called to attend Aldermans Hill, N13, after members of the public found a man with a stab wound to the neck.
They provided help to the victim, who it is believed may have been attacked in nearby Broomfield Park, and called police at 9.25pm on Saturday evening
He has been taken to hospital and is no longer in a life-threatening condition.
Police are in the process of informing his next of kin about the incident.
A police cordon is in place and the investigation is in its early stages.
Following the incident, a male self-presented at a north London police station and was arrested on suspicion of attempted murder in connection with the incident.
This male also presented with a stab wound, not believed to be life-threatening, and has been taken to hospital in the custody of officers for treatment.
Anyone with information is asked to Call 101, quote CAD7831/26May. Or Crimestoppers anonymously on 0800 555 111