Most studies of nonpharmacological interventions have used a combination of medications in experimental and control groups to improve cognitive functioning or to control symptoms, but the results have been inconsistent with respect to the effects of single nonpharmacological interventions on cognitive functioning in older patients with Alzheimer's disease. The aim of this study was to assess the effect of a single nonpharmacological intervention on cognitive functioning in older adults with mild-to-moderate Alzheimer's disease. We conducted a systematic review and meta-analysis in the first week of January 2024, searching eight electronic databases for articles that reflect on non-pharmacological interventions in Alzheimer's disease published between January 1, 1986, and December 31, 2023. All included articles had to be randomized controlled trials. The primary measure was the change in cognitive function before and after the intervention. Data were extracted by two authors and quality was assessed using the Cochrane Handbook. With the exception of the Montreal Cognitive Assessment (MoCA) scale [MD=2.99, 95% CI (-0.66,6.63)], the differences between the intervention group and the control group were significant for all the remaining scales, namely, the Mini-Mental State Examination (MMSE) [SMD=0.65, 95% CI (0.15,1.15)], Activity of Daily Living Scale (ADL) [MD=-2.30, 95% CI (-3.63,0.97)], Quality of Life in Alzheimer's Disease Scale (QoL-AD) [MD=5.03, 95% CI (2.27,7.78)], Neuropsychiatric Inventory (NPI) [MD=-2.16, 95% CI (-3.86,0.46)], and Alzheimer's Disease Assessment Scale-cognitive score (ADAS-cog) [MD=-5.21, 95% CI (-7.89,2.54)]. Subgroup analysis revealed that the most effective intervention was exercise therapy, followed by repetitive transcranial magnetic stimulation. On the other hand, music therapy was not found to be effective. Current evidence suggests that nonpharmacological interventions can be used to improve cognitive functioning in older adults with mild-to-moderate Alzheimer's disease. This study was registered in PROSPERO (registration number: CRD42024497247).