Self-diagnosis is becoming more common as the internet is gradually becoming a popular source for adults seeking health information online. The definition of self-diagnosis using online resources in this study refers to the act of an individual using internet-connected devices, such as computers or smartphones, to try to identify their medical conditions or health problems without seeking guidance from a qualified healthcare professional. To gain insight into these observable facts, there is a desire to ascertain the prevalence of adults in the area who utilise the Internet and Apps for self-diagnosis and to understand their perspectives regarding this practice. The prevalence, perception, and experience of utilising online resources for self-diagnosis among adults were surveyed in Klang Valley, Malaysia. An online Google survey was conducted from 4th to 10th October 2023, targeting the adult population residing in Klang Valley, Malaysia. Convenience sampling was used, and the survey link was shared with easily accessible contacts, i.e. to the students’ WhatsApp chat groups. This approach allowed the fast recruitment of respondents within the time constraints of this study. Additionally, the association between sociodemographics and the experience encountered by those seeking online resources to aid self-diagnosis was examined. A total of 55.5% of respondents (n = 238, N = 429) have used online resources for self-diagnosis. Most of them (n = 235, 98.7%) reported favourable experiences with information obtained online. However, they deem it unsafe and prefer consulting healthcare professionals for quicker symptom resolutions. While examining the sociodemographic factors, those aged 18–30, females, and of Chinese ethnicity self-diagnose using online resources more than the other groups, mostly via search engines. Our analysis of sociodemographic characteristics with experience of online self-diagnosis revealed that education level was the only statistically significant factor (p = 0.045). It is recommended that health education initiatives begin at the primary education level with an emphasis on reliable resources to seek information for medical conditions online. To date, there has been a lack of scholarly articles on self-diagnosis in Malaysia. Therefore, these preliminary research findings together with the validation of the questionnaire used can serve as a foundation for future comprehensive studies by local researchers.