We have investigated the effects of changing Sb fractions and misorienting InP(0 0 1) substrates on InAs 1− x Sb x quantum structures grown by metal-organic vapor-phase epitaxy (MOVPE), with the aim of obtaining small quantum dots (QDs) with 1.55-μm emission. At medium Sb content, InAsSb tended to form quantum wires (QWRs) with widths of less than 20 nm along the [ 1 1 ¯ 0 ] direction on InP(0 0 1), which was due to the surfactant effect. The [ 1 1 ¯ 0 ] size of these narrow InAsSb QWRs decreased as the miscut angles toward the [ 1 1 ¯ 0 ] direction of the vicinal InP(0 0 1) substrates was increased, and the InAsSb shapes changed from QWRs into QDs. Nearly 1.55-μm-emitting InAs 0.61Sb 0.39 QDs with lateral sizes of 20–30 nm embedded in InGaAsP barriers were fabricated on a vicinal substrate with a miscut of 5°, which will enable InP-based QD-telecom device applications.