This study investigates the impact of an online workbook on the attitudes of 245 second language (L2) Spanish learners toward this pedagogical tool over two consecutive semesters. The treatment consisted of four hours of classroom instruction and one set of online homework per week, during two consecutive semesters. Students' attitudes toward the electronic workbook were measured by means of a survey administered after eight months of exposure to the workbook. The qualitative data of the survey was compared to quantitative data from two different language assessment tests. The results of these tests indicated a significant increase in grammar scores. These results are consonant with the positive findings of student perceptions about the online workbook obtained in this and previous studies, emphasizing its benefits in terms of accessibility to the material, user-friendliness, and instant error feedback. More importantly, most students praised the usefulness of the online workbook for language learning, particularly in the areas of grammar and vocabulary acquisition. Despite participants' mostly positive attitudes, the survey also revealed some negative aspects of the use of the online workbook, such as the amount of time needed to complete the online exercises. This paper addresses these issues, and provides suggestions to overcome this type of problem.