We have previously shown that casein kinase (CK) Iafrom mammalian brain phosphorylates 14-3-3fandsisoforms on residue 233. In the present study, we show that CKIaassociates with 14-3-3 bothin vitro andin vivo. The interaction between CKIaand 14-3-3 is dependent on CKIaphosphor-ylation, unlike centaurin-a1 (also known as ADAP1), which binds to unphosphorylated CKIaon the same region.