Cycloaddition (CA) reactions have attracted recently strong interest not only for the preparation of linear polymers but also for the synthesis and modification of dendritic architectures. This review focuses mainly on the potential of various cycloaddition reactions in the field of dendrimers and especially hyperbranched polymers. The [4 + 2] Diels–Alder cycloaddition, [2 + 2 + 2] CA as well as 1,3-dipolar CA reactions including “click chemistry” will be addressed, and advantages of these reactions will be highlighted. High selectivity, thus high tolerance towards additional functionalities, high yields and often moderate to mild reaction conditions distinguish CA reactions from the often applied classical high-temperature polycondensation type reactions used mainly to synthesize hyperbranched polymers. Thus, besides the high potential in the synthesis and modification of perfectly branched dendrimers, cycloaddition reactions proved also very suited to prepare new types of hyperbranched structures.