This study investigated how resource-demanding reading tasks and stressful conditions affect 1st-language (L1) and intermediate 2nd-language (L2) reading comprehension. Using the attentional control theory framework (Eysenck, Derakshan, Santos, & Calvo, 2007), we investigated the roles of central executive working memory (WM) resources, reading task difficulty, trait reading anxiety, and social evaluative stress on L1 and L2 readers' comprehension. Eighty-six L2 Spanish readers and 70 L1 English readers were tested for comprehension using noninference (fact), bridging inference, and pragmatic inference questions under either no-stress or social-evaluative stress conditions. Stress reduced processing efficiency (producing longer reaction times) for L2 readers who were high in reading anxiety and increased processing efficiency for L1 readers who were high in WM capacity. Stress did not affect reading effectiveness (accuracy). Thus, stress only impaired reading efficiency when task difficulty was high due to high inferential complexity or reading in an L2 and when anxious thoughts competed for limited central executive WM resources. Theoretical and practical implications of these findings are discussed.