The aim of this study was to examine the situational associations of reading-related task values and efficacy beliefs with achievement emotions, and whether these associations are moderated by reading difficulties (RD). The sample comprised 128 Finnish sixth-grade students (66 with no reading difficulties [No RD], 31 with mild reading difficulties [Mild RD], and 31 with severe reading difficulties [Severe RD]) who were randomized to complete either a non-challenging or challenging reading task. Students reported their reading-related task values (attainment and interest) and efficacy beliefs right before and their achievement emotions both before and after performing the reading task. The results revealed that the associations of task values and efficacy beliefs with achievement emotions were moderated by RD and task difficulty. High attainment value was related to more positive and less negative emotions, especially for students with Severe RD. In turn, high interest value and efficacy beliefs were related to more positive emotions during the task, especially for students with No RD or Mild RD. Finally, among all students, higher interest value in the face of a non-challenging reading task and higher efficacy beliefs in the face of a challenging reading task were related to less negative emotions. The results provide a novel understanding of the role of RD in the situational associations between reading-related motivation and achievement emotions.