BACKGROUND: Dementia is a major public health priority due to its increasing prevalence and the considerable burden it places on individuals living with the condition and their carers. Internet-based tools can help carers and the people they support to manage daily tasks, access resources and support, track health data, and connect with health care professionals. However, the benefits of these tools will only be realized if the intended users have access to the internet and are confident in its use. OBJECTIVE: This study aimed to examine the patterns of internet access and use among dementia carers in Australia and the people they support. METHODS: A cross-sectional survey of carers providing informal support to a person diagnosed with dementia and living in the community was conducted. Carers were recruited through geriatric clinics, aged care providers, and community organizations between July 2018 and June 2020. Consenting carers self-completed a multitopic survey that included study-specific questions about their access to the internet, confidence using the internet, and whether the person with dementia they support was able to use the internet. Multivariate regression analysis identified sociodemographic factors associated with carers' internet access. RESULTS: A total of 172 carers (consent rate 47%) with an average age of 71.8 (SD 10.91) years completed the survey. Most carers (126/155, 81%) had access to the internet; however, 31% (47/153) reported they were not at all confident in using it. The likelihood of carers having access to the internet decreased with carers' age (OR [odds ratio] 0.87, 95% CI 0.80-0.96; P=.003). Male carers were 4 times more likely to have internet access than female carers (OR 4.32, 95% CI 1.00-18.6; P=.05). Similarly, carers with private health insurance (an indicator of individual socioeconomic status) were 8 times more likely to have internet access than those without private health insurance (OR 8.45, 95% CI 2.74-26; P<.001). Only 17% (29/166) of carers perceived that the person with dementia they support was able to use the internet independently or with assistance. CONCLUSIONS: Despite high rates of internet access among carers, significant age, gender, and socioeconomic disparities were found, and a notable proportion lacked confidence in its use. Internet use among people with dementia was limited. The digital disparities identified in this study suggest that targeted training to build digital literacy to effectively use internet resources and co-design new technologies is needed. The findings further highlight that in this digital era, alternative methods to deliver dementia care and resources are essential to accommodate those who are unable to access or are less comfortable using the internet.