Students at the University of Colorado Boulder have also been told to avoid "white trash" costumes and anything that portrays a particular culture as "over-sexualised"- which the university says includes dressing up as a geisha or a "squaw" (indigenous woman).
They are also asked not to host parties with offensive themes including those with “ghetto” or "hillbilly" themes or those associated with "crime or sex work."
In the letter sent by a university official students are asked to consider the impact that their costumes could have.
Christina Gonzales, the dean of students, wrote: "Making the choice to dress up as someone from another culture, either with the intention of being humorous or without the intention of being disrespectful, can lead to inaccurate and hurtful portrayals of other people's cultures.
Additionally some students have also hosted offensively-themed parties that reinforce negative representations of cultures as being associated with poverty ("ghetto" or "white trash/hillbilly"), or with crime or sex work."
A university spokesman called cowboy costumes a "crude stereotype"
Students at the University of Minnesota- Twin Cities have also been asked to make sure their Halloween costumes are politically correct.
In a letter officials said: "please keep in mind that certain Halloween costumes inappropriately perpetuate racial, cultural, and gender stereotypes."
The move comes at a time when pressure is mounting on one of the most famous American football teams to change their name because of the offence it causes Native Americans.
The campaign for the Washington Redskins to change their name is building momentum, because the term redskin is deemed to be a racist insult.
Earlier this month President Obama said the team should think about changing their name.