Quasicrystals exhibit low thermal and moderate electrical conductivity, accompanied by a relatively high absolute magnitude of thermopower, which makes them suitable candidates for use as thermoelectric devices. Theoretical explanations of electrical and thermal conductivity and thermopower of two representative members of the Al-Cu-Fe icosahedral quasicrystal family (i-Al62Cu25.5Fe12.5 and i-Al63Cu25Fe12) are given. Their figures of merit are relatively low compared with the best-known thermoelectric materials.