Abstract: Chatbots are becoming increasingly popular due to their benefits in saving costs, time, and effort. This is due to the fact that they allow users to communicate and control different services easily through natural language. Chatbot development requires special expertise (e.g., machine learning and conversation design) that differ from the development of traditional software systems. At the same time, the challenges that chatbot developers face remain mostly unknown since most of the existing studies focus on proposing chatbots to perform particular tasks rather than their development. Therefore, in this paper, we examine the Q&A website, Stack Overflow, to provide insights on the topics that chatbot developers are interested and the challenges they face. In particular, we leverage topic modeling to understand the topics that are being discussed by chatbot developers on Stack Overflow. Then, we examine the popularity and difficulty of those topics. Our results show that most of the chatbot developers are using Stack Overflow to ask about implementation guidelines. We determine 12 topics that developers discuss (e.g., Model Training) that fall into five main categories. Most of the posts belong to chatbot development, integration, and the natural language understanding (NLU) model categories. On the other hand, we find that developers consider the posts of building and integrating chatbots topics more helpful compared to other topics. Specifically, developers face challenges in the training of the chatbot’s model. We believe that our study guides future research to propose techniques and tools to help the community at its early stages to overcome the most popular and difficult topics that practitioners face when developing chatbots.