Background This study tested model‐driven predictions regarding working memory's role in the organizational problems associated with ADHD. Method Children aged 8–13 (M = 10.33, SD = 1.42) with and without ADHD (N = 103; 39 girls; 73% Caucasian/Non‐Hispanic) were assessed on multiple, counterbalanced working memory tasks. Parents and teachers completed norm‐referenced measures of organizational problems (Children's Organizational Skills Scale; COSS). Results Results confirmed large magnitude working memory deficits (d = 1.24) and organizational problems in ADHD (d = 0.85). Bias‐corrected, bootstrapped conditional effects models linked impaired working memory with greater parent‐ and teacher‐reported inattention, hyperactivity/impulsivity, and organizational problems. Working memory predicted organization problems across all parent and teacher COSS subscales (R2 = .19–.23). Approximately 38%–57% of working memory's effect on organization problems was conveyed by working memory's association with inattentive behavior. Unique effects of working memory remained significant for both parent‐ and teacher‐reported task planning, as well as for teacher‐reported memory/materials management and overall organization problems. Attention problems uniquely predicted worse organizational skills. Hyperactivity was unrelated to parent‐reported organizational skills, but predicted better teacher‐reported task planning. Conclusions Children with ADHD exhibit multisetting, broad‐based organizational impairment. These impaired organizational skills are attributable in part to performance deficits secondary to working memory dysfunction, both directly and indirectly via working memory's role in regulating attention. Impaired working memory in ADHD renders it extraordinarily difficult for these children to consistently anticipate, plan, enact, and maintain goal‐directed actions.