The objective of this research is to investigate the effect of aliphatic amine chain lengths on shape memory polymers (SMPs) properties of benzoxazine resin. Bisphenol-A, paraformaldehyde, and different aliphatic amine chain lengths at 1:4:2 mol ratio are reacted at 120 °C for an hour. The synthesized samples are represented as BA-xMA, where x is the number of C atoms ranging from 6–18. It was found that shape fixity ratio (Rf) increased with short aliphatic chain, conversely to recovery ratio (Rr). Therefore, the self-copolymerization of poly(BA-xMA/BA-a)s are developed to improve the fixation ability. Interestingly, the cyclability of the copoly(BA-12dda/BA-a) at 60/40 is significantly enhanced reaching 34 cyclability where the Rr remains almost 100 %. Furthermore, the copoly(BA-12dda/BA-a) exhibits multiple-shape memory behavior resulting from a wide range of transition temperatures. The selfcopolymerization of benzoxazine reduces molecular complexity, enhances compatibility, and simplifies preparation steps, making benzoxazine-based SMPs highly promising for advanced shape memory polymer applications.