Research skills are important for university graduates, but little is known about undergraduates' motivation for research. In this study, self-efficacy beliefs and intrinsic motivation for several research activities were measured three times during an undergraduate research project (N = 147 students). In order to promote self-efficacy for writing and collaboration, a collaboration script was developed and tested on half of the students. Twelve students were interviewed three times to gather in-depth information about motivational and self-efficacy beliefs. All measures except intrinsic motivation for research increased significantly during the project. Interview results suggest that enactive mastery and positive social interdependence promoted self-efficacy. Feelings of relatedness seemed to promote intrinsic motivation for writing. Lack of autonomy and low perceived relevance may explain why motivation for research remained stable. The script had no impact on self-efficacy beliefs. Relatedness, autonomy and positive social interdependence may boost motivation for research, but more evidence is needed.