This study aims at investigating how task sequencing affects second-language learners’ attention to linguistic items during communicative interaction. Thirty intermediate learners of Japanese are asked to engage in two types of tasks (jigsaw and opinion exchange tasks) in sequence. Previous research reports that cognitive complexity affects learners’ attention to form in the jigsaw task but not in the opinion-exchange task. For each task, one group worked on a simplest task, complex task, and highly complex task, while the other group worked on three highly complex tasks. Learners’ attention to form during each task-based interaction was measured by counting Language-Related Episodes (LRE) (Swain & Lapkin, 1998). The results showed that in the jigsaw task, LRE gradually increased irrespective of the sequencing arrangements. On the other hand, the simple to complex task arrangement yielded a significant increase in the third task, while the repletion of highly complex tasks resulted in consistently low frequency of LRE over three tasks These findings contradicted the prediction of the Cognitive Hypothesis (Robinson, 2003) that argues that complex tasks affect learners’ focus on form, and the effects of task sequencing on learners’ focus on form depends on task type.