Effectiveness of individual and group-based neuropsychological interventions on cognitive aspects of dyslexia in young adults was evaluated. Dyslexic adults were randomly assigned into individual intervention (n = 40), group intervention (n = 40), or wait-list control group (n = 40). The interventions focused on cognitive strategy learning, supporting self-esteem, and using psychoeducation. Cognitive performance and symptoms were assessed via psychometric testing and self-report questionnaires at baseline, after the intervention/wait-list control time at 5 months and at 10 months. And, 15 months post intervention long-term status was checked via mailed inquiry. Wait-list control group also received an intervention after the 5-month control period. No significant effects were found in primary self-report outcome measures. Both interventions had a positive effect on a measure of processing speed and attention and the effect remained after the 5-month follow-up period. In self-reported cognitive symptoms, a positive trend was evident in self-reported reading habits. Furthermore, minor self-evaluated benefits reaching up to 15 months post intervention were found. There were no significant differences between the results of individual and group intervention as both interventions improved cognitive performance. The results indicate that a structured neuropsychological intervention could be effective in ameliorating dyslexia-related cognitive symptoms in young adults.