Older adults with subjective cognitive decline (SCD) have increased prospective risk of declining to mild cognitive impairment and dementia. Persons with SCD present with self- and sometimes informant-reported declines in cognitive function in the context of intact neuropsychological performance. Without objective evidence of cognitive impairment, emphasis then lies with subjective reports of cognition in prospectively discriminating persons with SCD from healthy older adults. However, ascertainment of sources of individual difference in the validity and meaning of cognitive complaints among healthy older adults has only recently emerged in the literature. Furthermore, examining the interrelationships of subjective and objective measures of cognition—particularly experimental measures—could improve discrimination of older adults at increased risk for dementia from healthy peers. We recruited healthy older adults (65 to 80 years) with SCD (n = 16) and healthy controls (n = 25). Self- and informant ratings of cognition were examined in relation to one another and as a function of objective, performance-based measures from the computerized multi-source interference task (MSIT), which includes both low- and high-cognitive control conditions. For healthy controls, self- and informant-reported complaints were positively associated. Compared with the healthy group, the SCD group significantly overreported complaints relative to their informants. Participants in the SCD group were also less accurate and more variable in their MSIT responses compared with healthy controls. In addition, informant-reported complaints predicted differences in the quality of across-trial performance variability for all individuals. Findings suggest that subjective report and sufficiently sensitive indices of cognitive performance provide complementary insights into the phenomenon of SCD.