The increased potential and speed of the Internet has changed the nature of sexual crimes against children. It enables individuals with a sexual interest in children to meet, interact, and engage in illegal activities. The literature review presented here aims to provide an overview of the current knowledge and understanding of trust and relationship development among users of online networks that are dedicated to the sexual exploitation and abuse of children. A systematic search using six databases was conducted to identify relevant literature from a psychological and a criminological perspective. Twenty-one studies met the inclusion criteria that centered around the key aspects of the literature review’s research question, namely, (i) child sexual exploitation and abuse, (ii) Dark Web platforms, (iii) online forums and networks, and (iv) trust and relationship development. Our findings reveal that the engagement in interpersonal communication and interactions with like-minded others serves various functions, including validation, normalization, and support, as well as access to expert advice, information, and material. Dark Web networks are high-stake and risky environments, where users have to manage a continuous flow of threats, with information about others and their trustworthiness being limited. The establishment and maintenance of trust is of social and technical relevance, and users have to navigate a number of demands and commitments. Findings are discussed in relation to theoretical and practical implications, as well as directions for future research.