Training and development research has a long tradition within applied psychology dating back to the early 1900s. Over the years, not only has interest in the topic grown but there have been dramatic changes in both the science and practice of training and development. In the current article, we examine the evolution of training and development research using articles published in the Journal of Applied Psychology (JAP) as a primary lens to analyze what we have learned and to identify where future research is needed. We begin by reviewing the timeline of training and development research in JAP from 1918 to the present in order to elucidate the critical trends and advances that define each decade. These trends include the emergence of more theory-driven training research, greater consideration of the role of the trainee and training context, examination of learning that occurs outside the classroom, and understanding training’s impact across different levels of analysis. We then examine in greater detail the evolution of 4 key research themes: training criteria, trainee characteristics, training design and delivery, and the training context. In each area, we describe how the focus of research has shifted over time and highlight important developments. We conclude by offering several ideas for future training and development research.