Students' engagement tends to decline as they progress through school (Anderman, Maehr, & Midgley, 1999; Eccles et al., 1993; Harter, Whitesell, & Kowalski, 1992; National Research Council and the Institute of Medicine, 2004; Yazzie-Mintz, 2010) and disengagement is linked with negative school outcomes such as dropping out of school, retention, failing to earn a diploma, lower grades, and decreased learning (Christenson et al., 2012; DiPerna, Volpe, & Elliot, 2002; Skinner et al., 2009). Youth with ADHD are an at-risk group for lower levels of emotional and behavioral engagement (American Psychiatric Association, 2000). This study investigated whether teacher instructional style (i.e., autonomy support and structure) predicts student engagement and disengagement utilizing an existing dataset collected from 52 students, and their parents and teachers from Dunedin, New Zealand. Student participants met DSM-IV criteria for ADHD, and ranged from 5 to 11 years of age. Class-wide, teacher-provided structure was measured by the Classroom Environment Scale Rule Clarity, and Order and Organization subscales. Class-wide, teacher-provided autonomy support was measured by the Classroom Environment Scale Innovation, Teacher Support, and Teacher Control subscales. Students' emotional engagement in school was measured by Teacher Report Form Working Hard, Happy, Withdrawn, and Anxious/Depressed T-scores. Correlational and multiple regression analysis were used to answer the study's research questions. Results from this study include findings that increased teacher control and lower ADHD severity significantly predicted greater student work effort (engagement). Student age and ADHD severity, and teacher-provided order and organization (structure) were found to significantly predict increased happiness (engagement). Higher teacher-provided structure in the form of rule clarity, order, and organization were found to significantly predict decreased student withdrawn and depressed behaviors (disengagement). In addition, lower teacher-provided order and organization (structure) and higher ADHD severity together were found to significantly predict increased anxious and depressed student behavior (disengagement). If replicated, findings from the current study could inform future intervention research by indicating the components of teachers' instructional styles that may be most influential in engaging students with ADHD in school.