This study evaluated a professional development intervention that stemmed from a university-district partnership and was developed through participatory action research. Baseline and postintervention survey items showed participating school psychologists' (n = 57) knowledge related to youth suicide improved reliably immediately after the intervention in all content knowledge areas. At 9-month follow-up, participants (n = 41) retained knowledge gains relevant to assessment and intervention strategies, whereas knowledge relevant to prevention and postvention activities declined. Increases in participants' confidence in their abilities to execute different suicide-related professional activities and in their confidence in working with diverse youth in relation to suicide risk maintained over time. At follow-up, 87% of participants who had received referrals for suicidal students reported accessing products from the professional development, compared with 40% of practitioners without the impetus of a suicidal student. Participants rated the professional development to be between "mostly" and "very" useful in facilitating their work with suicidal youth. (Contains 5 tables.)