Background <p>There is a paucity of research examining subjective cognitive change in healthy young and midlife (Y/ML) adults.</p> Objective <p>The aim of this study was to compare subjective cognitive change (both improvement and deterioration; SCC) between healthy Y/ML adults and individuals with mild traumatic brain injury (mTBI) and investigate factors that may be associated with SCC in YML adults.</p> Method <p>The sample comprised 111 healthy Y/ML adults and 72 age-matched individuals with mTBI who completed measures of SCC, psychological status and objective cognitive function.</p> Results <p>Analyses revealed that 81% of Y/ML adults believed their cognition was no different or better than 4 weeks prior, compared to only 41% of the mTBI group. There was no robust linear association between any measure of cognition or psychological status and SCC in the Y/ML adults (<i>p</i>&gt;.05).</p> Conclusions <p>Many healthy Y/ML adults believe their cognition to be improving over time, at least somewhat (34%).</p>