L2 vocabulary acquisition is of much importance to L2 learners and has long been the hot topic in the field of applied linguistics. Stimulated by the Technical Feature Analysis (TFA) and the Involvement Load Hypothesis (ILH) in particular, a large body of research has attempted to find the relative efficacy of various tasks in facilitating L2 vocabulary acquisition. However, there is a paucity of research regarding the relative effectiveness of the ILH and the TFA in accounting for the task type effects on L2 vocabulary acquisition. Therefore, the present study attempts to compare the relative effectiveness of the ILH and the TFA. The two main research questions are stated as follows: 1. How does task type (reading comprehension with glosses, gap filling, rewording and composition) affect EFL vocabulary acquisition? 2. Which better explains the relative effectiveness of tasks (reading comprehension with glosses, gap filling, rewording and composition) in facilitating EFL vocabulary acquisition, the Involvement Load Hypothesis (ILH) or the Technical Feature Analysis (TFA)? This study employed one-way ANCOVA (analysis of covariance) design with the between-subject factor being task type and the covariate being EFL vocabulary knowledge. The dependent variable was EFL vocabulary acquisition, which included two dimensions, i.e., word form recognition and passive word meaning recall. The EFL vocabulary knowledge posttests included the immediate and delayed posttests. After completing the EFL vocabulary knowledge (vocabulary size) test, 117 non-English major freshmen were randomly assigned to one of four learning tasks, i.e., reading comprehension with glosses (an index of 1 in the ILH versus an index of 5 in the TFA), gap filling (an index of 2 in the ILH versus an index of 7 in the TFA), rewording (an index of 3 in the ILH versus an index of 6 in the TFA) and composition (an index of 3 in the ILH versus an index of 8 in the TFA). The total task time required for the different groups was held constant. Then, on completion of the respective tasks, the participants were required to take the immediate posttests of word form recognition and passive meaning recall. One week after the immediate posttest, all the four groups took the delayed posttests. All the data collected were valid.