This systematic review evaluates published evidence on oral hygiene interventions conducted in Alzheimer’s disease (AD) patients. PubMed, Embase, Cochrane Library, CINAHL, Dentistry & Oral Sciences Source, and Web of Science were searched for articles published up to 19 April 2021. The main outcomes of interest were the Plaque index score (PI), oral health knowledge of participants or their caregivers, and behaviors and attitudes towards oral hygiene. Study quality was assessed using the Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies of the National Institutes of Health. The study was conducted under PROSPERO registration code CRD42021247733. Two studies met the inclusion criteria. One was a pre-post study conducted in Brazil, and the other was a prospective cohort study carried out in China. The sample sizes of these studies were 29 and 168, respectively. Both studies were carried out in institutionalized patients and presented a significant loss to follow-up. The PI and gingival index scores both improved after the application of the respective interventions, yet the differing methodologies used precluded further comparisons. The studies were deemed to be of good and regular quality, respectively. Despite the need for more comprehensive interventions to ensure a better oral health status and a higher quality of life for AD patients, an alarming lack of studies have been conducted in this population.