This study aims to summarize the research history of H. G. Underwood and examines research trends both before and after the Korean liberation. Before the liberation, there were seven studies on Underwood, of which the studies by L. H. Underwood(1918) and George L. Paik(1934) continue to have great influence today. Of Underwood’s work, it was found that the ecumenical movement was highly valued by researchers. After the liberation, 22 books, 86 articles, and 30 master’s and doctoral theses were published. Research on Underwood temporarily increased following a series of events, including the return of the Underwood family to the US in 2004, the completion and publication of the Underwood resource book in 2010, and the 100th anniversary of Underwood’s death in 2016. By subject area, studies examined a variety of topics including Underwood’s life, early mission work, theology, educational activities, documentary movements, modernization, and Korean studies. More recently, historians and scholars of Korean Studies have shown greater interest in Underwood than theologians. With declining interest in Underwood among theologians, the number of thesis papers on Underwood has been decreasing over the past 15 years.