Reading comprehension is a complex cognitive task crucial to success in formal education and everyday life activities. Working memory (WM) and associated executive processes have been shown to be implicated in reading comprehension abilities. The aim of the present study was to assess the efficacy of a program for improving reading comprehension skills based on reading activities that require WM and associated executive processes. The study involved 48 third-graders (8-9 years old), who were assigned to three groups: a trained group that received training on reading comprehension and on the mechanisms related to this ability; an active control group that attended extra in-school activities designed to improve children's reading comprehension; and a passive control group that only attended normal lessons. The training program consisted of ten sessions conducted in the classroom, focusing on WM and associated executive functions embedded in reading comprehension activities. The efficacy of the training was examined in terms of both specific improvements in reading comprehension and WM, and transfer effects to more ecological reading comprehension and nonverbal reasoning tasks. Long-term gains were also examined after 2 months. The results showed that the training was effective in directly improving the children's reading comprehension and WM, with some maintenance effects too, while it elicited limited gains in the more ecological reading comprehension task, and no transfer effects on nonverbal reasoning. Overall, the present findings suggest that training involving the use of WM and its executive processes during reading comprehension activities is a promising approach to sustaining reading comprehension.