The structure of a monosubstituted ferrocene derivative of which the flexible spacer is located between the ferrocenyl and mesogenic groups, ω-[4-(4-methoxyphenoxycarbonyl)phenoxycarbonyl]butyl 4-ferrocenylbenzoate was determined by the X-ray diffraction method. The -C4H8- chain introduced as a flexible spacer is an all-transconformation. The molecule is slightly bent around the ester group to the phenyl ferrocenyl group in order to form a rod-like structure. The molecular geometry is a rod-like feature, and two cyclopentadienyl rings exhibit an eclipsed conformation rather than a staggered one. As a result, this bent structure can lead to efficient packing because it is suitable to make up a bulk of unsubstituted cyclopentadienyl ring, and may play an important role in the appearance of the liquid crystal phase. The molecules are arranged in layers just like the smectic phase of the liquid crystals.