This comparative case study examines how parallel deployments impact on UN peace operations’ legitimacy. It focuses on if and how the two French military operations, Serval and Barkhane, affected the legitimacy of MINUSMA. A theoretical framework on relational dynamics of parallel deployments and on legitimacy was established. The first step was to analyze the legitimacy of Serval/Barkhane. Thereafter, the relational dynamics between Serval/Barkhane and MINUSMA were analyzed. Last step was discussing how the legitimacy of respective military operation and the relational dynamics could explain the parallel legitimacy dynamics. Using assessment reports by different institutions, a qualitative within-case analysis was conducted to identify changes in legitimacy. The study shows that both Serval and Barkhane had a negative impact on MINUSMA’s legitimacy but in different ways. Serval affected the legitimacy negatively by creating high expectations that MINUSMA could not fulfill. Barkhane affected the legitimacy negatively by making the UN peace operation seem partial due to its association with the counterterrorist Barkhane.