This study aims to investigate the effect of DDL on English lexico-grammar learning by Korean middle school students with respect to the types of learning approach (deductive vs. inductive DDL), the student’s level of English (low vs. high level), and the complexity of lexico-grammar items (simple vs. complex). A total of five experimental lessons were given to 36 students divided into two groups: one group received the lessons through the deductive DDL approach and the other group through the inductive DDL approach. The study found that both inductive and deductive DDL were effective in the learning of English lexico-grammar by the Korean middle school students. However, deductive DDL was more effective for the high level students, while inductive DDL was more appropriate for low level students. In addition, both deductive and inductive DDL were effective for teaching simple lexico-grammar items, but deductive DDL was more effective for teaching complex ones. Most of the participants showed positive responses about DDL and expressed a view that they were able to learn the meanings as well as the forms of target lexico-grammar items.