Introduction: Behavioral and psychological symptoms of dementia (BPSD) is the most prominent and distressing manifestation for older persons with dementia (PWD) and caregivers. Aromatherapy has demonstrated its effectiveness in managing BPSD in various studies. However, previous studies and systematic reviews have obtained inconsistent findings, and a review of qualitative studies is yet to be conducted. Method: A mixed-methods systematic review with a convergent segregated approach was performed to evaluate the effectiveness of aromatherapy in improving the BPSD and quality of life (QoL) of PWD and in relieving the distress and burden of caregivers, as well as its safety for PWD. Both published and unpublished quantitative and qualitative studies written in English and Chinese between January 1996 and December 2020 were retrieved from 28 databases, including MEDLINE, EMBASE, and Web of Science, based on the prespecified criteria. The methodological quality was assessed by using critical appraisal tools from the Joanna Briggs Institute. Quantitative synthesis, qualitative synthesis, and integration of quantitative and qualitative evidence were performed. Results: A total of 12 randomized controlled trials, 10 quasi-experimental studies, and 2 qualitative studies were included in the review. Some inconsistent findings regarding the effectiveness of aromatherapy in reducing the severity of BPSD were observed. Some studies reported that aromatherapy significantly improved the QoL of PWD and relieved the distress and burden of caregivers, promoted a positive experience among caregivers, and had very low adverse effects on PWD (with aromatherapy inhalation reporting no adverse effects). Conclusion: Aromatherapy, especially in the inhalation approach, could be a potentially safe and effective strategy for managing BPSD. However, more structuralized and comparable studies with sufficient sample size, adherence monitoring, and sound theoretical basis could be conducted to obtain conclusive findings.