Blast exposure in Operation Enduring Freedom/Operation Iraqi Freedom often results in mild traumatic brain injury (mTBI), physical, and psychological conditions for Service members. Symptoms associated with mTBI can compromise safe return to duty, but are difficult to assess. Development of an end-user informed functional assessment is an important step in advancing improved return-to-duty decision-making. In 2009, a team of military and civilian occupational and physical therapy researchers were funded by the U.S. Army Medical Research Materiel Command to develop such a measure, since labelled the Assessment of Military Multitasking Performance. The development process involved stakeholder interviews, iterative literature reviews, expert consultation and a subject matter expert summit. This process resulted in a battery of dual- and multi-task scenarios designed to challenge mTBI vulnerable systems, including executive function, attention, memory, high level balance, vestibular function, gaze stability, and physical exertion during military-relevant tasks. 35 interviewees provided guidance [military leadership, researchers, and medical personnel (physicians, therapists, and neuropsychologists), commanders, and civilian experts]; 4 content experts provided methodological advice; and 15 stakeholders/content experts attended an advisory summit to further guide assessment development. The multidisciplinary process resulting in the Assessment of Military Multitasking Performance (AMMP) is described, highlighting end-user priorities, shaped by expert interdisciplinary collaboration. Following refinement and validation, the AMMP will advance evidence-driven return-to-duty decision making, aiming to distinguish those with acceptable task proficiency from those whose mTBI symptoms put themselves and others at risk.