This study seeks to address the complexity of impacts of the learning environment on the efficiency of adult learning in professional development training. The systematic approach to the learning environment and its constituents provides the opportunity for analyzing the factors of key importance with special focus on the choice of the training methods and techniques that facilitate the learning process. The study presents the philosophical and epistemological reasoning on the one hand and the empirical evidence based on the findings of quantitative and qualitative research carried out by the author in the specific context of the civil service profession in the United States. The synthesis of research results is provided with an emphasis on practical applications in a highly encouraging learning environment that facilitates interaction, experiential learning, reflection, and enhances improved workplace performance. The comparative approach resulting from the author's experiences in the Hungarian civil service training highlights the opportunities for benchmarking.