This study investigated how middle school students' comprehension was impacted by reading social studies texts online with a pop-up dictionary function for every word in the text. A quantitative counterbalance design was used to determine how 129 middle school students' reading comprehension test scores for the pop-up dictionary reading differed from test scores for reading hard-copy texts or an online text without the dictionary. The pop-up dictionary reading was shown to be a statistically effective method for improving student test scores. The results suggest pop-up dictionaries may provide a helpful intervention for increasing middle-level learners' reading comprehension. (Contains 2 tables.)