Paraphimosis is caused by inflammation and narrowing of the foreskin. The inflammation may be caused by infection and is possibly associated with poor personal hygiene. Occasionally inflammation develops after direct trauma to the area, which results in swelling. Uncircumcised males and those who may not have been appropriately or completely circumcised are at risk.

The strictured foreskin is retracted behind the glans penis and left there for some period of time. Blood flow from penis is blocked, and the glans becomes swollen. The increased size of the glans then prevents the foreskin from being returned to its extended position. If paraphimosis is left untreated, the blood flow to the glans is impaired; lack of blood flow to the glans may result in loss of the penis tip.

Paraphimosis usually occurs most often in children and the elderly.