Tooth loss remains a major oral health problem among older adults and may impair mastication, nutritional intake, communication, and quality of life. Although adequate knowledge of oral health maintenance may support preventive behaviors, evidence regarding its relationship with tooth loss among community-dwelling older adults in Surabaya remains limited. This study aimed to determine the association between oral health maintenance knowledge and the number of missing teeth among older adults attending Posyandu Lansia Sekar Arum, Kertajaya, Surabaya. An analytical observational study with a cross-sectional design was conducted among 54 older adults aged 65 years and above selected using simple random sampling from 62 registered individuals. Oral health maintenance knowledge was assessed using a validated structured questionnaire, while tooth loss was determined through direct oral examination. Data were analyzed descriptively and using the Chi-square test, with Cramér’s V used to estimate the strength of association. The results showed that 46 participants (85.2%) had poor oral health maintenance knowledge, whereas 44 participants (81.5%) had lost more than ten teeth. Cross-tabulation demonstrated that 41 of 46 participants (89.1%) with poor knowledge had experienced tooth loss exceeding ten teeth. The Chi-square analysis demonstrated a statistically significant association between oral health maintenance knowledge and tooth loss (χ² = 36.42, df = 6, p < 0.001), with Cramér’s V = 0.58, indicating a strong association. These findings indicate that inadequate oral health maintenance knowledge is associated with greater tooth loss among older adults in the study population. Strengthening age-appropriate oral health education and preventive services through community-based health programs may support better oral health practices and preservation of natural teeth among older adults.