AbstractCalmodulin regulated spectrin‐associated protein 1 (CAMSAP1) is a vertebrate microtubule‐binding protein, and a representative of a family of cytoskeletal proteins that arose with animals. We reported previously that the central region of the protein, which contains no recognized functional domain, inhibited neurite outgrowth when over‐expressed in PC12 cells [Baines et al., Mol. Biol. Evol. 26 (2009), p. 2005]. The CKK domain (DUF1781) binds microtubules and defines the CAMSAP/ssp4 family of animal proteins (Baines et al. 2009). In the central region, three short well‐conserved regions are characteristic of CAMSAP‐family members. One of these, CAMSAP‐conserved region 1 (CC1), bound to both βIIΣ1‐spectrin and Ca2+/calmodulin in vitro. The binding of Ca2+/calmodulin inhibited spectrin binding. Transient expression of CC1 in PC12 cells inhibited neurite outgrowth. siRNA knockdown of CAMSAP1 inhibited neurite outgrowth in PC12 cells or primary cerebellar granule cells: this could be rescued in PC12 cells by wild‐type CAMSAP1‐enhanced green fluorescent protein, but not by a CC1 mutant. We conclude that CC1 represents a functional region of CAMSAP1, which links spectrin‐binding to neurite outgrowth. image Knockdown of the cytoskeletal protein CAMSAP1 using siRNA inhibited NGF‐induced (nerve growth factor) neurite outgrowth from PC12 cells, and axon production by cerebellar granule cells in culture. This activity is linked to a spectrin‐ and Ca2+/calmodulin‐binding region (CC1), since over‐expression of isolated CC1 inhibited neurite production from PC12 cells. We previously showed that CAMSAP1 binds microtubules at the C‐terminal CKK domain. Our data indicates CAMSAP1 is a cytoskeletal interconnector required for neurite and axon production.