Parental alienation was first recognized in New York custody cases by the Appellate Division in Entwistle v. Entwistle, 61 A.D.2d 380 (2d Dep't 1978). There, the mother consented to the entry of judgment of divorce after the parties stipulated that she would retain custody of the children, subject to visitation rights of the husband. The stipulation also provided that she "shall have the right to remove her residence together with the children to Greenwich, Conn., subject to the approval of the Court." Within one month after the judgment was entered, she remarried, took the children, and moved to Illinois, without informing the husband of her or the children's location. She then commenced a proceeding in Illinois to register her New York divorce judgment and to redefine the husband's visitation rights. The husband made an application in Supreme Court to punish her for contempt for willfully failing to comply with the visitation provisions of the judgment of divorce and to transfer custody of the children to him, based upon the visitation improprieties. The Appellate Division directed that a hearing be held with respect to the father's application. In its decision, it stated that "the respondent's very act of preventing the two children of tender age from seeing and being with their father is an act so inconsistent with the best interests of the children as to, per se, raise a strong probability that the mother is unfit to act as custodial parent." See also Rosenstock v. Rosenstock, 162 A.D.3d 702 (2d Dep't 2018).

Parental alienation must be distinguished from "parental alienation syndrome," a disorder termed by child psychiatrist Richard A. Gardner in "Recent Trends in Divorce and Custody Litigation," Academy Forum, Volume 29, Number 2, Summer, 1985, p. 3-7. According to Gardner, parental alienation syndrome occurs when one parent deliberately or unconsciously attempts to alienate a child from the other parent. The parent who programs the child brings about the destruction of the bond between the other parent and the child. It is characterized by a cluster of eight symptoms that appear in the child. These include a campaign of denigration and hatred against the targeted parent; weak, absurd, or frivolous rationalizations for this deprecation and hatred; lack of the usual ambivalence about the targeted parent; strong assertions that the decision to reject the parent is theirs alone (the "independent-thinker phenomenon"); reflexive support of the favored parent in the conflict; lack of guilt over the treatment of the alienated parent; use of borrowed scenarios and phrases from the alienating parent; and the denigration not just of the targeted parent but also to that parent's extended family and friends. Gardner, R.A., The Parental Alienation Syndrome, Second Edition (1998).

Parental alienation syndrome is not generally accepted in the scientific community, as it is not an approved term or diagnosis in the field of psychiatry. No New York court has allowed the admission of testimony concerning parental alienation syndrome. It is not a diagnosis included in the Fifth Edition of the Diagnostic and Statistical Manual of Mental Disorders. See Montoya v. Davis, 66 N.Y.S.3d 350, n.3 (3d Dep't 2017).