Dreams of Halloween signify that you are embracing and bringing awareness to the different masks you wear and to the social roles you play. This powerful dream is about embracing your shadow, the aspects of yourself which are the most difficult to love because your subconscious mind recognizes the value in fusing, unifying and integrating all aspects of yourself. Consider the feeling tone. See Mask, Shadow, Ghost and Integration Dreams.... Strangest Dream Explanations
A dream of Halloween represents the temporary adoption of a new persona, where you feel less inhibited and more comfortable to freely express yourself. Also see “Candy” and “Halloween Party”... My Dream Interpretation
If you dreamed of attending a Halloween party where everyone was in costume except you, this is a warning against false friends.
To dream that you wore a costume to the party signifies that you are putting on a false face toward others. Your true self is not being revealed and you are not being completely honest with people around you.... My Dream Interpretation