Objective <p>This meta-analysis aimed to evaluate the efficacy of non-invasive neuromodulation techniques in improving global cognitive function in patients with&#xa0;Alzheimer's disease (AD) and Mild cognitive impairment (MCI). Non-invasive brain stimulation includes repetitive transcranial magnetic stimulation (rTMS), transcranial alternating current stimulation (tACS), and transcranial direct current stimulation (tDCS), and to compare the efficacy of the three.</p> Methods <p>Searches were conducted in five databases: PubMed, Embase, Web of Science, Cochrane and Scopus. We searched these databases for randomized controlled trials on non-invasive neuromodulation techniques treatment for AD and MCI up to April 10, 2025, to conduct meta-analyses and network meta-analyses. The primary outcome measures were the scores on the Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), and Alzheimer's Disease Assessment Scale–Cognitive Subscale (ADAS-cog). PROSPERO registration: CRD420251120672.</p> Results <p>This study included 77 articles. Compared with the control group, rTMS, tACS, and tDCS can all improve the overall cognitive function of participants. The results of the meta-analysis showed that rTMS and tDCS can increase MMSE and MoCA scores and decrease ADAS-cog scores (p &lt; 0.05).&#xa0;Network meta-analysis reveals tDCS is more effective than rTMS on MMSE and MoCA, but less effective on ADAS-cog.</p> Conclusions <p>rTMS, tACS, and tDCS can all improve the overall cognitive function of patients with AD and MCI, and are effective and safe treatment methods. When assessed using the MMSE and MoCA scales, the results show that the tDCS is superior to rTMS.</p>