Background Well trained nurses are expected to influence their workplaces after completing their training courses. In Cambodia, a high-skill training program has been given for nurses to make them more qualified since 2011. After completing the program, we conducted an immediate post-training study in 2014. In this long-term, post-training study, we evaluated the program’s effect on nursing faculty and clinical preceptors and identified factors influencing the long-term outcomes.Methods This long-term, post-training study took the form of embedded, single-case design. It incorporated focus group discussions (FGDs) for 26 trainees, key-informant interviews for 11 institutional managers, and teaching document reviews. Then, we conducted a thematic analysis using Kirkpatrick’s four levels of training evaluation. We evaluated the latter two elements as long-term outcomes, behavior (changes in trainees’ practice and applying learning to practice), and results (the trainees’ behavior effect on trainees’ organization or department). After that, we assessed factors influencing the long-term outcomes using Bronfenbrenner’s ecological systems theory.Results We identified five themes at the behavior level according to program type. They were 1) improved teaching and learning activities, 2) built capacity of nursing faculty and clinical nurses, 3) improved clinical practicum, 4) strengthened clinical nursing management, and 5) involved in professional development activities. At the results level, we identified three themes as long-term outcomes from an institutional development aspect. They were 1) enhanced institutional capacity, 2) improved students’ learning and behavior, and 3) strengthened clinical performance. The major influencing factors for the above eight themes were 1) institutional managers’ support, 2) continuous networking among trainees, and 3) national policy.Conclusions The upgrading program had a favorable effect on nursing faculty and clinical preceptors at the Kirkpatrick model’s behavior and results levels. Compared with the immediate post-training study findings, the perceived long-term outcomes became more strategically focused and demonstrated the training impact on a considerably broader scale within the workplace. These findings have implications for the monitoring and evaluation of nursing faculty development programs for its sustainable outcomes