Excerpted with permission from a longer version of this article, which can be found on the website Torah From Dixie.
Thanksgiving is a uniquely American holiday. It is no longer (and perhaps never was) a celebration affiliated with any particular religion or faith, although some in America celebrate with religious ceremonies….
The first and most significant issue in discussing whether it is halakhic [acceptable according to Jewish law] to celebrate Thanksgiving is whether it is permissible to eat a Thanksgiving meal, with the classical foods that American tradition indicates one should eat at this meal: turkey and cranberry sauce. Among the authorities of the previous generation, three different positions have been taken on this topic, and these three positions have each been accepted by various halakhic authorities of the current generation.
The Legal Background
However, before these three positions can be understood, a certain background into the nature of the prohibition against imitating Gentile customs must be understood. Tosafot [a medieval Talmud commentary] understands that two distinctly different types of customs are forbidden by the prohibition of imitating Gentile customs found in Leviticus 18:3. The first is idolatrous customs and the second is foolish customs found in the Gentile community, even if their origins are not idolatrous.
Rabbenu Nissim and Maharik disagree and rule that only customs that have a basis in idolatrous practices are prohibited. Apparently foolish–but secular–customs are permissible so long as they have a reasonable explanation (and are not immodest). Normative Halakhah follows the ruling of the Ran and Maharik.
The Approach of Rabbi Feinstein
Rabbi Moshe Feinstein has four published responsa [rabbinic rulings] on the issues related to celebrating Thanksgiving, all of which conclude that Thanksgiving is not a religious holiday but a secular one. The first responsum, written in 1953, discusses the deliberate scheduling of weddings and the like on religious holidays of other faiths. Rabbi Feinstein states: