Teaching is a stressful profession, and teacher stress has been shown to be associated with job dissatisfaction, attrition from the field, and negative outcomes for teachers and their students. A major contributor to teacher stress is disruptive student behavior. Given that students with or at-risk for attention-deficit/hyperactivity disorder (ADHD) demonstrate high rates of disruptive behaviors and are present in nearly every classroom, studying the connection between student ADHD symptoms and teacher stress may provide useful insights for better supporting teachers and their students. Aims of this study were to (1) assess the replicability of a previous finding that teachers rate their students with elevated ADHD symptoms to be more stressful to teach than students without these symptoms and (2) explore the extent to which key factors (i.e., overall work-related stress and student–teacher relationship quality) moderate the relationship between student ADHD symptoms and related teacher stress. Participants were 97 K-2nd grade teachers who completed an online survey about themselves and two male students in their classroom. Results showed that teachers report students with elevated levels of ADHD symptoms and impairment to be more stressful to work with than students who do not exhibit these symptoms (d = 1.52). Additionally, overall work-related stress and conflict in the student–teacher relationship exacerbated the relationship between student ADHD symptom severity and related teacher stress, whereas closeness in the student–teacher relationship mitigated this association. Implications of these findings and directions for future research are discussed.