<p>As the global population ages, understanding cognitive dysfunction, including Alzheimer’s Disease and other forms of dementia, is crucial. With the growing prevalence of these disorders, it is essential to identify and understand potential factors that maintain cognitive function and potentially delay severe cognitive dysfunction. This study examined the roles of repetitive negative thinking (RNT) and reflection in subjective cognitive dysfunction among older adults, with an additional consideration of their association with depressive symptoms. RNT, which is common in depression, has been associated with cognitive impairments. However, its unique influence on cognitive dysfunction is unclear. Conversely, reflection, considered to protect against adverse cognitive outcomes, is less explored. Using the Rumination Response Scale (RRS), we hypothesize that RNT may be more strongly linked to cognitive dysfunction than reflection, even when controlling for depressive symptoms. Two-hundred and seventy-six older adults (137 male, 139 female) from Japan participated in the study, providing measures of RRS-brooding (an index of RNT), RRS-reflection (an index of reflection), depressive symptoms, and self-reported cognitive dysfunction. The results showed higher reflection, but not RNT, was associated with greater subjective cognitive dysfunction [β = 0.28, <i>p</i> =.03], even after controlling for depressive symptoms. Importantly, the association between reflection and cognitive dysfunction demonstrated sex differences, with reflection significantly accounting for cognitive dysfunction in female [β = 0.46, <i>p</i> =.01] but not in male. These findings highlight the significance of evaluating specific subtypes of repetitive thoughts and sex differences when investigating the association with perceived cognitive dysfunction. Future research should continue to explore the mechanisms underlying these associations and the prevention and treatment of cognitive dysfunctions.</p>