Objectives: This pilot study evaluated the feasibility, acceptability, and preliminary outcomes of the Up-Res school-based resilience intervention designed for immigrant and refugee students in European secondary schools (Germany and Greece). Methods: A sequential explanatory mixed-methods design was implemented across four pilot schools in Germany and Greece. In the quantitative phase, 57 immigrant and refugee students (aged 12–15 years; 63.2% male) completed the 25-item Connor–Davidson Resilience Scale (CD-RISC-25) across three time points (PreTest, PosTest after Module 1, and final PosTest), with longitudinal changes analyzed using Friedman and post hoc Wilcoxon tests. In the qualitative phase, inductive thematic analysis was applied to teacher analytical reports, authorized student interview recordings, and digital reflection journals to evaluate implementation conditions and mechanisms of change. Results: Statistically significant longitudinal gains were observed across all resilience sub-dimensions (all p < 0.001), with overall resilience scores increasing from baseline (60.44 ± 12.72) to mid-intervention (68.88 ± 15.67) and final post-test (74.51 ± 15.90, W = 0.64). The qualitative findings supported these improvements through five key themes: growing student engagement, high contextual relevance of migration-sensitive materials, perceived skill gains (coping, emotion regulation, positive thinking), strengthened trust and willingness to seek adult help, and key practical considerations (pacing and group size). Conclusions: The Up-Res intervention is a feasible, acceptable, and contextually meaningful framework for enhancing psychosocial resilience and social connectedness among displaced youth. Translating abstract concepts into concrete, participatory activities, as well as adopting a strengths-based approach, can facilitate implementation in European educational settings.