Although online instruction has many potential benefits, technical difficulties are one drawback to the increased use of this medium. A repeated measures design was used to examine the effect that technical difficulties have on learning and attrition from voluntary online training. Adult learners (N = 530) were recruited online and volunteered to participate in a four-hour training program on using computer spreadsheets. Technical difficulties were inserted in some of the training modules in the form of error messages. Using multilevel modeling, the results indicated that the presence of these technical difficulties impaired learning, such that test scores were lower in modules where trainees encountered technical difficulties than in modules where they did not encounter technical difficulties. Furthermore, the effect on learning was greater among trainees who eventually withdrew from the course than among trainees who completed the course. With regards to attrition, pretraining motivation provided a buffer against dropping out, especially when trainees encountered technical difficulties. Learning also predicted attrition from the subsequent module, such that attrition was higher among trainees with low test scores in the previous module. The current study disentangles some of the implications of technical difficulties and suggests that organizations should provide trainees with the technical support required to overcome technical difficulties in training. Furthermore, the findings contribute to our theoretical understanding of the implications of interruptions on performance in online training.