Charter schools in the U.S. experience higher rates of student and teacher turnover than traditional public schools (TPS). Less is known, however, about principal turnover, despite the important role that a principal plays in a school's success. This paper evaluates principal turnover in New York City's charters and TPS during 2008-18. It finds that: (1) principal turnover is higher in charters than in TPS; (2) the charter-TPS turnover gap changes over time; (3) the gap may be smaller than previously thought; (4) higher turnover is "not" due to differences in student demographics between the two sectors; and (5) turnover is similar in low-performing charters and in low-performing TPS. Empirical research has found that principal turnover tends to negatively affect a school's performance. This paper's findings thus suggest, among others, that New York City charters--which are, in general, already more effective than the city's TPS--might further improve by reducing principal turnover.