Ashishkapoor7 wrote:The dinner was eaten by John and I .
The dinner was eaten by John and me.

Which one is correct and why.

Hi Ashish,

I moved the question to this forum.
Your sentence is what's known as a passive sentence, where the intended object is behaving like the subject.
Normally (in an active sentence), we'd say John and I ate the dinner, where the subject performing the action is "John and I".

In this passive sentence, the verb phrase is "was eaten"
Who or what was eaten? The dinner. So, the dinner is the subject here. This means "John and me" is the object. As such, we need "me"

Cheers,
Brent