Researchers have recently applied achievement goal theory to understand students' disruptive behaviors in educational settings (Agbuga, Xiang, & McBride, 2006; Kaplan & Maehr, 1999). They observed that students endorsing mastery goals (MG) reported fewer disruptive behaviors than students endorsing performance-approach and performance-avoidance goals (PApG and PAvG). This finding seems to suggest achievement goals are related to students' disruptive behaviors in school. However, disruptive behaviors in their work were self-reported. Therefore, there is a need to extend this line of research to objective measures of student disruptive behaviors as they have greater external or ecological validity than behavior rating scales (Nock & Kurtz, 2005). Consequently, this study investigated whether achievement goals students adopted in an after school physical activity program were related to their observed disruptive behaviors. As part of a larger study, 158 students in grades 3-6 completed a 15-item questionnaire assessing their achievement goals. All items were modified from previous research and subjected to factor analyses. Then, nine students, based on their achievement goal scores, were selected for observation. Among them were three high in MG (X = 4.53, SD = .23), three high in PApG (X = 4.86, SD = .23), and three high in PAvG (X = 4.86, SD = .11). Each of the nine students was videotaped individually for three consecutive 30-minute lessons, resulting in 27 lessons. Observation data revealed disruptive behaviors displayed by students high in MG, PApG, and PAvGs were 80 (12.55%), 338 (53. 07%), and 219 (34.38%), respectively. These results suggest students adopting a high MG displayed disruptive behaviors less frequently than students adopting either a high PApG or PApG. However, a chi-square analysis [χ2(2)= 3.52, p = .176] yielded no significant association between the two variables, which is inconsistent with previous findings (Agbuga et al., 2006; Kaplan & Maehr, 1999). One possible explanation for such a discrepancy might be that the nine students selected for this study were each observed for three consecutive 30-min lessons only. This frequency of observation may be inadequate to catch the relationships between achievement goals and disruptive behaviors among students. Another possibility could be that the number of students observed in the present study was too small. Therefore, future research is recommended to replicate this study with more lessons and a larger number of students to determine the nature of the relationship between achievement goals and observed disruptive behaviors in after-school physical activity programs.Keyword(s): elementary issues, physical education PK-12, youth-at-risk