Despite their importance, dynamic and diagnostic assessments (DigAs) have received little attention in phycological aspects of foreign language teaching and learning settings; therefore, this study compared the effects of dynamic and diagnostic assessment (DigA) on Afghan EFL learners' speaking fluency and accuracy (SFA), learning anxiety (LA), and cognitive load (CL). To do so, 90 Afghan EFL learners were recruited and assigned to two experimental groups (EGs), namely a dynamic assessment group (DAG), a DigAG, and a control group (CG). After that, the three groups were pretested on SFA, LA, and CL. Then, one EG was trained based on the DA, and the other EG was taught based on the DigA, while the CG received common speaking instruction. After finishing the instruction, all groups were given the posttests of SFA, LA, and CL to evaluate the impacts of the treatment on their performances. The findings of the one-way ANOVA test divulged that both EGs outflanked the CG on their posttests. In fact, using dynamic and DigA developed EFL learners' SFA and CL and reduced their LA. Though both EGs outflanked the CG, the DAG had better improvement than the DigAG on their posttests. At the end of the research, some implications were provided, and some suggestions were recommended for the next studies.