Despite over fifteen years of flipped classroom implementation, current literature does not provide any reliable, standardized rubric as a guideline to create or evaluate flipped classroom lessons based on effective flipped classroom design principles. In fact, at the time of this study, when an internet search for existing rubrics was conducted, there were no rubrics found. This is the first study to (1) fully characterize and (2) assess the reliability of a rubric for evaluating flipped classroom lesson plans.