Epoxy resins have high chemical and heat resistance, as well as good mechanical and thermal properties. Consequently, they have a wide range of industrial applications, including semiconductor encapsulants, adhesives, coatings, and automobile and aerospace parts.1,2 Epoxy polymers are generally synthesized by reacting epoxy resins with amine or maleic anhydride hardeners.3,4 It is known that epoxy polymers form three-dimensional networks and that the crosslinking density of these polymers depends on the number of glycidyl ether groups in the resin.5 When epoxy resins react with amine hardeners, one proton on the nitrogen atom of the hardener binds with one glycidyl ether to form a polymer network.6 Based on the location of functional groups in the molecule,7 amine hardeners can be categorized as poly(ether amines); polyamides; amidoamines; ethylene amine derivatives such as diethylenetriamine (DETA), triethylenetetramine (TETA), and lupasol; cycloaliphatic amines [bis(p-aminocyclohexyl)methane (PACM)) and diaminocyclohexane (DACH)]; and aromatic amines such as 4,40 -methylenediamine (MDA) and diaminodiphenyl sulfone (DDS). Extensive research has been carried out on amine hardeners for both petroleum-based and biobased epoxy resins.8 Jeffamine, a poly(ether amine), has long pot life, low viscosity, and flexible properties but has low crosslinking density and poor mechanical properties when cured with epoxy resins.9–۱۱ In the case of ethylene diamines such as DETA or TETA, controlling the reaction becomes difficult because of high reaction rates. Lupasol hardeners, one of the most widely used branched ethylene diamine derivatives, have many advantages over other ethylene amines but do not have good mechanical properties as they only have hyperbranched alkyl chains.12,13 Cycloaliphatic amines can be cured faster than poly(ether amines), but a disadvantage is that the resulting products are brittle.14 As aromatic amine derivatives cure slowly upon reacting with epoxy resins, they require high temperatures to form epoxy polymers. However, the cured polymers have a high glass-transition temperature (Tg) and good mechanical properties. Moreover, the polymers show high thermal stability and high activation energy of thermal decomposition, in addition to good adhesion onto substrates.15,16 In this study, aromatic xylylene functional groups were introduced into an ethylene diamine derivative precursor to yield an amine hardener with multiaromatic functionalized amines as well as a flexible ethylene diamine linker. By dynamic mechanical analysis (DMA), flexural strength measurements, and microcombustion calorimetry (MCC) methods, it was confirmed that the presence of xylylene groups leads to good mechanical properties, improved thermal stability, and excellent fire resistance.