Plant awareness disparity (PAD, formerly plant blindness) is the idea that students tend not to notice or appreciate the plants in their environment. This phenomenon often leads to naïve points of view, such as plants are not important or do not do anything for humans. There are four components of PAD: attitude (not liking plants), attention (not noticing plants), knowledge (not understanding the importance of plants), and relative interest (finding animals more interesting than plants). Many interventions have been suggested to prevent PAD, but without an instrument shown to demonstrate valid inferences to measure PAD, it is difficult to tell whether these interventions are successful or not. We have developed and validated the Plant Awareness Disparity Index (PAD-I) to measure PAD and its four components in undergraduate biology students. The study population was 74.32% female and 69.08% white, indicating that the need for further analysis is necessary if this instrument is to be used in a more diverse student population. We collected validity evidence based upon text content, response processes, and internal structure. Our findings demonstrate that our instrument generates reliable inferences regarding PAD with a Cronbach's alpha of 0.884 and a six-factor structure that aligns conceptually with the four components of PAD.