Knowledge of Alzheimer's disease (AD) among healthcare staff influences important aspects of care and is associated with better patient outcomes. This study aimed to assess the knowledge of AD among healthcare professionals working in government hospitals and healthcare centers in Jeddah, Saudi Arabia. This cross-sectional study used an online questionnaire to assess Alzheimer's disease knowledge using the Alzheimer's Disease Knowledge Scale (ADKS). Participants also self-rated their knowledge and reported their experience in dementia care and training. The study included 231 healthcare professionals, with 61.5% males and 38.5% females. Medical professionals demonstrated significantly higher mean ADKS score = 19.84 compared to pharmacy, nursing, and allied health professionals (P <
.05). Other factors, such as gender, age, workplace setting, years of experience, and formal dementia training, showed no significant impact on ADKS scores (P >
.05). However, participants with additional dementia-related learning experiences, such as workshops or self-directed study, had significantly higher scores (P <
.05). A notable finding was the discrepancy between self-assessed and actual knowledge. Among those who rated themselves as "very knowledgeable," only 10% achieved a very good ADKS score, while more than half failed the test. Conversely, those who rated themselves as having poor knowledge often performed better than expected, with many achieving good or very good ADKS scores 44.3% and 13.1%, respectively. This study highlights significant disparities in Alzheimer's disease knowledge among healthcare professionals in Jeddah, with medical staff showing higher understanding. Tailored educational programs are needed to address these gaps and improve dementia care.