Search engine advertising (SEA), in which businesses (or advertisers) bid on keywords and pay search engine providers (eg Google) to get a secure place on the first page of search results, is a prominent source of revenue for search engine companies, and an effective method for businesses to promote their visibility on the Web. SEA is a complex and dynamic form of advertising and managing it effectively is still a challenge for many businesses, particularly smaller businesses. Building upon resource-based theory, this study has developed a context-specific model for understanding advertisers' competency factors that influence SEA effectiveness. Using structural equation modelling and survey data collected from 142 businesses, this research has found that SEA effectiveness is influenced by organizations' ability to manage keywords and bids, ability to analyse and monitor outcomes, advertising expertise, commitment to SEA task, and the use of external experts. Moderating relationships between the factors have been examined, and the implications of the findings for both academics and practitioners have been discussed.