We reported a synthetic protocol of polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) copolymers via dehydrobromination and click coupling reactions. The PS block (acetylene-PS) was prepared by anionic polymerization and end-functionalized with an acetylene group. The other PMMA block was synthesized by an atom transfer radical polymerization (ATRP) of MMA using an azido-initiator. It was found, unexpectedly, that the click reaction of acetylene-PS and the bromide-ended PMMA using Cu(I)Br yielded a byproduct with double the molecular weight of the product (PS-b-PMMA). This was attributed to the coupling of the bromide ends of block copolymers. This problem could be avoided by a dehydrobromination of the PMMA block into the olefin end (azido-PMMA-ene) using tetra-n-butylammonium fluoride (TBAF) at room temperature. Due to the mild dehydrobromination condition and the weak basicity of TBAF, no hydrolysis of PMMA esters occurred. After the click coupling of acetylene-PS and azido-PMMA-ene, the excess PS was removed by further click reaction using insoluble PS resins surface-functionalized with azide groups.