A novel chiral organic radical 2-{4′-((S)-2″-methylbutoxy)phcnyl}-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (1) and its metal complex, [1·Mn(II)(hfac)2]nwere synthesized and characterized. The radical1crystallizes in the orthorhombic space groupP212121(No. 19) witha= 11.494(3) Å,b= 25.328(3) Å,c= 6.1281(5) Å,V= 1748.0(4) Å3. The complex [1·Mn(II)(hfac)2]ncrystallizes in the same space group witha= 14.081(1) Å,b= 15.940(1) Å,c= 16.075(1) Å,V= 3608.1(4) Å3. X-ray crystal structure analysis of the complex revealed the formation of a helical-chain structure. The oxygen atoms of the radical1are ligated to two different manganese ions incisposition and exhibit the δ configuration in [1·Mn(II)(hfac)2]n. The magnetic measurements revealed that this chiral complex behaves as a ferrimagnet below TC= 4.5 K. It is characterized by a strong intrachain exchange correlation, the ratio between the intrachain and interchain exchange interactions being about 10−5.