Digital libraries continue to be an important source for indigenous content and research output in developing countries, especially in the context where traditional distribution mechanisms failed. It is therefore useful for continual research to maintain and enhance our standing on the topic and to improve ways of making digital libraries more usable and sustainable to the user community. It is with this effect that this study on the success factors of digital libraries was conducted, with the objective to identify and validate a set of critical success factors (CSFs) for digital library implementation in developing countries. To address this, a quantitative exploratory research design was employed using a web-based survey questionnaire as the data collection technique. A total of 56 item statements associated with the Technology-Organisation-Environment (TOE) framework were developed and respondents were asked about their Perceived Importance and Actual Practices of those factors in digital library implementation. Digital libraries in Africa were sampled and an identified 155 digital libraries from this continent were obtained from OpenDOAR, with 111 sample size representative of the respondents. Based on a 70 percent response rate expectation, invitations were sent to respondents representing the digital libraries. After almost six months, there was a 67.7 percent response rate with 105 usable questionnaires obtained. This study revealed eight CSFs for digital library implementation in ranked order - Content, Architecture, People, Process, Standards, Location and Time, Policy and Advocacy. They are the salient factors that would not only assist to attain sustainable digital library development and implementation, but also provide guidance to library practitioners in appropriate decisions for digital library adoption. It may also help libraries to accomplish their digital library mission in the most cost effective way.