The crystallization of alpha-olefin molecular bottle-brushes occurs via side-chain crystallization exclusively, which is fundamentally different from the common chain folding process occurring in linear polyolefin crystallization. However, the exact mechanisms of side-chain crystallization have not been explored to date. Herein, we report the melting and crystallization behaviors of a series of poly(alpha-olefin) homopolymers with a syndiotactic backbone (sP alpha O) and side-chain lengths (N-sc) ranging from 4 to 16 carbons. Only sP alpha Os with N-sc >= 10 are able to crystallize into a hierarchical morphology, as revealed by a combination of SAXS, SALS and optical microscopy measurements. A monotonic increasing dependence on N-sc of the thermal properties (melting temperature, enthalpy, and entropy of fusion) and of the crystallinity is observed on the sP alpha Os, which reveal that the odd-even effect on those properties (as observed on n-alkanes) does not operate in alpha-olefin bottlebrushes. The side chains in the crystallizable sP alpha Os arrange into a nematic rotator phase, similar to atactic poly(1-octadecene) recently reported [Macromolecules 2018, 51 (3), 872-883]. The bottlebrush molecules pack into fibril bundles made of several molecules packed into a hexagonal lattice. On a larger scale, density fluctuations give rise to a bicontinuous microstructure with characteristic size on the order of 1 mu m.