Introduction: This study aims to investigate the selection of information sources and to identify factors associated with the resource selection of undergraduate students for academic search tasks. Also, user perceptions of some factors, such as credibility, usefulness, accessibility and familiarity, were examined to classify resources by their characteristics. Method: A self-generated diary method was employed with 233 undergraduate students in achieving their academic search tasks. Analysis: The collected diary data were analysed both qualitatively and quantitatively. A qualitative analysis was used to explore factors influencing resource selection, while a quantitative analysis was used for investigating the characteristics of resources. Results: This study reaffirmed recent information usage trends that online sources are preferred by university students in their academic searches. This study identified twenty nine factors in four different dimensions, including information type, resource feature, search strategy, and interaction with others. Moreover, perceptions of users were investigated quantitatively focusing on usefulness, credibility, accessibility, familiarity with source, satisfaction, and intention of continuous use. Conclusions: Multiple factors are influencing the resource selection of undergraduate students and those factors vary in different types of sources in academic search tasks. The findings of the study suggest some insights in how to guide undergraduates to choose better information resources for their academic search tasks. (Contains 9 tables and 2 figures.)