Improving Worker Safety in Contracting Act of 2021 This bill requires the Department of Defense (DOD) to develop and provide annual training and guidance to acquisition officials, contracting officers, and current and potential contractors. Such training must include information regarding (1) the authorities and requirements of DOD officials to consider workplace safety and health information in the pre-award, award, and contract performance phases of the contracting process; and (2) the availability of relevant contractor safety information on the Occupational Health and Safety Administration website. The Government Accountability Office must submit a report to DOD and Congress on the health and safety records of DOD contractors. DOD must develop a system for assigning safety performance ratings for its contracts in industries that have relatively high rates of occupational injuries (e.g., manufacturing). Beginning in FY2023, DOD contracting officials must (1) assess contractor safety performance at the time of contract completion in industries that have relatively high rates of occupational injuries, and (2) consider information about prospective contractors' records of safety performance as a factor in awarding contracts in industries that have relatively high rates of occupational injuries.