I’ve heard the phrase “between you and I” many times. Often, it seems to be used when someone is trying to be more proper or formal. I even saw it in an episode of Lost Girl, spoken by a character trying to be very proper.
Unfortunately, “between you and I” is NEVER correct. It is always “between you and me.”
A way to think about it is to think of a cult leader and his followers. Only certain types of people will ever join a cult. Think of prepositions as cult leaders. Only certain types of pronouns will follow this leader. These pronouns are in the objective case, i.e. followers.
The pronoun “I” can never be in the objective (object) case. It is always nominative (subject of the verb). It will not follow a preposition, drink its Kool-Aid, or burn in its church.
So, next time you want to be formal or proper, say, “Between you and me.”
(I think this issue is part of a larger discussion of “____ and I,” but we’ll get to that in another post.)
Nominative Case Pronouns Object Case Pronouns (Followers)