Chatbots are increasingly offered as an alternative source of customer service. For users to take up chatbots for this purpose, it is important that users trust chatbots to provide the required support. However, there is currently a lack in knowledge regarding the factors that affect users’ trust in chatbots. We present an interview study addressing this knowledge gap. Thirteen users of chatbots for customer service were interviewed regarding their experience with the chatbots and factors affecting their trust in these. Users’ trust in chatbots for customer service was found to be affected (a) by factors concerning the specific chatbot, specifically the quality of its interpretation of requests and advise, its human-likeness, its self-presentation, and its professional appearance, but also (b) by factors concerning the service context, specifically the brand of the chatbot host, the perceived security and privacy in the chatbot, as well as general risk perceptions concerning the topic of the request. Implications for the design and development of chatbots and directions for future work are suggested.