Several interventions have demonstrated efficacy in improving social outcomes for children with autism, but they often are not used in schools. This study examined individual and organizational factors associated with the use of a research-informed social engagement intervention, Remaking Recess, for children with autism in elementary schools. A total of 28 school personnel from 12 schools in 5 districts in the northeastern United States participated. Schools were randomized to (1) training in Remaking Recess only or (2) training in Remaking Recess with implementation support. School personnel rated their attitudes about evidence-based practices, organizational readiness, and fidelity. Independent observers rated school personnel's fidelity at baseline (pre-intervention training) and exit (post-intervention training). The results suggest that self-rated fidelity was lower when staff perceived the use of Remaking Recess was required; however, observer-rated fidelity was lower when staff rated Remaking Recess as appealing. In addition, self-rated fidelity was higher when there was a sufficient number of staff, positive individual growth, and organizational adaptability. The results also indicated higher observer-rated fidelity when staff perceived a positive influence over their coworkers. The results suggest that both individual (attitudes) and organizational (influence, staffing, growth, adaptability) characteristics may affect implementation success in schools. A collaborative decision-making approach for evidence-based practice use is recommended.