This systematic review compiles recent empirical studies to evaluate the effects of negotiated syllabi on learning outcomes, specifically language skills, motivation, autonomy, self-efficacy, self-esteem, and anxiety in English as a Foreign Language (EFL) and English for Specific Purposes (ESP) environments. Following the structure of the PRISMA guidelines, 21 sources were considered, with 19 meeting the inclusion criteria. Thematic analysis was used to interpret the findings. Results showed that negotiated syllabi significantly boost learners’ motivation, participation, autonomy, and self-efficacy, for the most part. Regarding language skills, findings were mixed; while writing, speaking, and overall language performance tend to improve, reading comprehension results vary depending on the level of negotiation. Students generally view the process positively; however, challenges exist in implementation due to institutional constraints and a lack of actively interested students. The negotiated syllabus is a valuable educational tool for fostering a user- and learner-centered approach. It, however, requires a step-by-step negotiation process, teacher openness, and adaptation of negotiation mechanisms tailored to the learner’s alertness level.