NIH Clinical Trial Diversity Act of 2023 This bill sets out requirements to increase the diversity of clinical trial participants and requires other activities to foster participation in clinical trials. As a condition of approval from the National Institutes of Health (NIH) for a clinical trial investigating a drug, device, or behavioral intervention, a sponsor's application must include certain information related to diversity in its trial, such as goals for recruiting and retaining trial participants, plans for achieving the recruitment and retention goals and implementing less-burdensome clinical trial follow-up requirements, and requirements for researchers and other individuals involved with the trial to complete education and training about diversity in clinical trials. A sponsor must also annually share demographic data of clinical trial participants with the NIH. The NIH must publish on its website information about the diversity of and other information concerning the clinical trials it funds. If a sponsor fails to meet its diversity goals or related requirements, the sponsor must develop and implement a strategic plan to increase the diversity of the clinical trial participants. Further, the NIH and the Food and Drug Administration must carry out a national campaign to increase awareness about the need for diverse clinical trials. The bill also requires studies on barriers to participation in clinical trials. The Government Accountability Office must study actions taken by federal agencies to address such barriers while the NIH must study regulations that govern reimbursements of out-of-pocket expenses of and incentives for clinical trial participants.