A female prison psychologist who began a courtship with a 15-year-old inmate met him for sex on the day of his release from juvenile detention and later bore him a child.

Catherine McKeehan, who is 18 years older than the father of her child, has been struck off by the Psychology Tribunal of NSW for three years for professional misconduct.

She was was working as a counsellor at Reiby Juvenile Justice Centre in 2007 when she met a boy, referred to as ''client A''.

She began supplying the minor with a weekly ration of tobacco and trading love letters.

The tribunal heard evidence of the psychologist's letters, which included the statements "I love you" and "the only reason I come to work is to see you".