This study obtained empirical evidence regarding the effects of using printed dictionaries (PD), pocket electronic dictionaries (PED), and online type-in dictionaries (OTID) on English vocabulary retention at a junior high school. A mixed-methods research methodology was adopted in this study. Thirty-three seventh graders were asked to use all three types of dictionaries to finish reading tasks, and then were tested not only immediately after the reading tasks, but also two and four weeks later. Questionnaires and interviews were used to examine the participants' attitudes and reflections after using the three types of dictionaries. Results indicate that although electronic dictionaries (OTID and PED) temporarily attract junior high school students' attention, PD helps them retain target words more effectively. Spending more time working with a PD apparently helped participants retain target words better. In contrast, the fast retrieval speed of an electronic dictionary might not impress the word forms and meanings onto junior high school students to such a significant degree. Electronic dictionaries could thus be used as a gateway to arouse students' interest to use dictionaries, while printed dictionaries could be used to help students retain the word forms and meanings.