Background: ASSIP flex is a structured, low-threshold brief therapy for individuals with suicidal behavior. As a flexible treatment approach, it can be delivered in inpatient, outpatient, and home settings. This study examines its feasibility, acceptability, and clinical application in routine practice. Method: In an observational pre-post study, 105 patients (53.8 % women; M = 38.8 years, SD = 15.2) were interviewed before (t0) and after (t1) the ASSIP flex brief intervention. Sociodemographic characteristics, feasibility aspects, and clinical variables were assessed. In addition, nine therapists evaluated implementation and acceptability. Results: ASSIP flex was mainly recommended by professionals (57.3 %) and showed high acceptability, with its adaptability across different treatment settings cited as a key advantage. Patients demonstrated a significant reduction in suicidal ideation (t104 = 4.5, p 0.001) and depressive symptoms (t104 = 6.0, p 0.001), as well as an increase in self-efficacy (t104 = -2.3, p 0.05). Higher perceived effectiveness of ASSIP flex correlated with lower suicidal ideation (r = -0.28, p 0.01) and depressive symptoms (r = -0.29, p 0.01), as well as increased self-efficacy (r = 0.22, p 0.05). Conclusion: ASSIP flex is a versatile treatment option for individuals with suicidal behavior. The results confirm its potential as a promising addition to existing care structures and its ability to address a critical gap in post-attempt care.