ABSTRACT Error-free chromosome segregation requires dynamic control of microtubule attachment to kinetochores, but how kinetochore–microtubule interactions are spatially and temporally controlled during mitosis remains incompletely understood. In addition to the NDC80 microtubule-binding complex, other proteins with demonstrated microtubule-binding activities localize to kinetochores. One such protein is the cytoplasmic linker-associated protein 2 (CLASP2). Here, we show that global GSK3-mediated phosphorylation of the longest isoform, CLASP2α, largely abolishes CLASP2α–microtubule association in metaphase. However, it does not directly control localization of CLASP2α to kinetochores. Using dominant phosphorylation-site variants, we find that CLASP2α phosphorylation weakens kinetochore–microtubule interactions as evidenced by decreased tension between sister kinetochores. Expression of CLASP2α phosphorylation-site mutants also resulted in increased chromosome segregation defects, indicating that GSK3-mediated control of CLASP2α–microtubule interactions contributes to correct chromosome dynamics. Because of global inhibition of CLASP2α–microtubule interactions, we propose a model in which only kinetochore-bound CLASP2α is dephosphorylated, locally engaging its microtubule-binding activity.