Background <p>This study aimed to assess the knowledge, attitudes, and practices (KAP) of orthodontic patients regarding periodontal health.</p> Methods <p>A multicenter cross-sectional survey was conducted between December 2024 and May 2025 at Jinan Stomatological Hospital. Structured questionnaires were administered to collect demographic information and to evaluate participants’ KAP scores related to periodontal health. A cutoff value of 70% of the maximum possible score was applied to define adequate knowledge, positive attitude, and proactive practice.</p> Results <p>A total of 2,638 valid questionnaires were included in the final analysis. Among the respondents, 1,636 (62.02%) were female, with a mean age of 31.59 ± 10.44 years. A total of 1,853 participants (70.24%) were undergoing orthodontic treatment for the first time. The mean scores for KAP were 12.54 ± 3.94 (possible range: 0–18), 46.00 ± 4.13 (possible range: 10–50), and 39.30 ± 5.01 (possible range: 9–45), respectively. Structural equation modeling (SEM) demonstrated that knowledge was positively associated with attitude (β = 0.493, <i>P</i> &lt; 0.001) and practice (β = 0.753, <i>P</i> &lt; 0.001), and that attitude was positively associated with practice (β = 1.087, <i>P</i> &lt; 0.001). In addition, knowledge showed an indirect association with practice mediated by attitude (β = 0.535, <i>P</i> &lt; 0.001).</p> Conclusion <p>Orthodontic patients exhibited insufficient knowledge but maintained generally positive attitudes and proactive practices regarding periodontal health. These findings highlight the importance of understanding periodontal health literacy among orthodontic patients within a descriptive KAP framework.</p> Clinical trial number <p>Not applicable.</p>