The task-modulated emotion–cognition–performance interaction warrants greater scholarly attention due to its pedagogical potential for effective L2 instruction and learning. However, implications for L2 speaking remain underexplored. This study investigates the effects of tasks with varying cognitive demands on English-as-a-Foreign-Language learners’ task emotions (anxiety, enjoyment, and boredom), as well as the separate and combined effects of these emotions and attention control on L2 speech performance across these tasks. Results showed that task demands were effective in affecting task emotions, with the least demanding task eliciting the lowest anxiety and the highest enjoyment. Among these emotions, only task anxiety significantly predicted breakdown fluency. Furthermore, higher attention control capacity was associated with greater syntactic complexity under moderate or high enjoyment, and with higher accuracy under conditions of high boredom, highlighting the interactive role of task emotions and attention control in L2 speech production. These findings hold significant insights for task-based language teaching researchers and L2-speaking practitioners, particularly in informing task design that addresses both learners’ emotional needs and cognitive challenges.