Rachel McAdams and marijuana do not mix well!

On Monday, the "Midnight in Paris" star stopped by "Jimmy Kimmel Live"  to promote her latest flick, "To The Wonder," where she shared her experience using cannabis for the first time as a sleeping aid.

The redheaded beauty said she tried using when her grocer promised it would help her battle insomnia ... and instead, it made McAdams hallucinate!

Check out the clip above to see what she said what it was like being high for the first time.

After having a negative experience with THC, Rachel went back to her grocer to voice her complaints with the green substance ... when the actress realized that her beloved market man was indeed a "stoner."

"I said 'I’m really upset,' he was like 'Oh it didn’t put you to sleep?' And then I realized, I really looked at him and his eyes were like this big. I was like 'You're a stoner!'"

Marijuana may not be McAdam's thing, but red hair definitely is!

How great does she look with her radiant new 'do?

Think this was the first time Rachel's used marijuana, or was she just being dramatic? Sound off below!

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