Parental alienation is defined as a mental state in which a child, usually one whose parents are engaged in a high-conflict separation or divorce, allies himself strongly with one parent (the preferred parent) and rejects a relationship with the other parent (the alienated parent) without legitimate justification. Parental alienation may affect men’s mental health: a) parental alienation negatively influences mental health of male children and adolescents who are victims of parental alienation. Alienated children/adolescents display guilt, sadness, and depressed mood; low self-esteem and lack of self-confidence; distress and frustration; lack of impulse control, substance abuse and delinquent behavior; separation anxiety, fears and phobias; hypochondria and increased tendency to develop psychosomatic illness; suicidal ideation and suicide attempt; sleep and eating disorders; educational problems; enuresis and encopresis; b) parental alienation negatively affects the mental health of adult men who were victims of parental alienation when they were children and/or adolescents. Long-term effects of parental alienation include low self-esteem, depression, drug/alcohol abuse, lack of trust, alienation from own children, divorce, problems with identity and not having a sense of belonging or roots, choosing not to have children to avoid being rejected by them, low achievement, anger and bitterness over the time lost with the alienated parent; c) parental alienation negatively influences mental health of men who are alienated from their children. Fathers who have lost some or all contact with their children for months or years following separation or divorce may be depressed and suicidal.