Despite the increasing significance of written communication, there is limited research into spelling therapy for adults with acquired dysgraphia. Existing studies have typically measured spelling accuracy as an outcome, although speed may also be important for functional writing. As spelling is relatively slow, effortful and prone to errors in people with dysgraphia, minimising errors within therapy could be a factor in therapy success. This within-participant case-series study investigated whether errorless and errorful therapies would differ in their effects on spelling speed and accuracy for four participants with acquired dysgraphia. Matched sets of words were treated with errorless or errorful therapy or left untreated. Results were collated one week and five weeks after therapy. Both therapy approaches were successful in improving spelling accuracy. For three participants, equivalent gains were demonstrated following errorless and errorful therapy. One participant made significantly greater improvements in spelling accuracy following errorless therapy. The effects were maintained five weeks later. There was no significant difference in post-therapy spelling speed between the two therapy conditions. The results of this study suggest that both errorful and errorless therapies can be effective methods with which to treat spelling in adults with acquired dysgraphia. © 2014 Taylor & Francis.