The effect of copolymer architecture on the phase behavior of a ternary polymer blend containing two homopolymers and a copolymer as well as the interfacial characteristics of this blend in the phase-separated state are examined using Monte Carlo simulation. At low copolymer concentration (ca. 1%), the phase transition from miscible to immiscible does not change within the resolution of the simulation for any of the copolymer structures studied here, which include block, random, and alternating architectures. It is found, however, that the copolymer does migrate to the biphasic interface in the phase-separated regime and that the configuration of the copolymer at the interface is a function of sequence distribution within the copolymer. This effect is interpreted in terms of the efficiency of the copolymer to strengthen the biphasic interface. These results suggest that both block and alternating structures show promise as interfacial modifiers, while the purely random copolymer will have the weakest effect on interfacial strengthening. It is also found that a variation of the sequence distribution away from a purely random structure can dramatically affect the ability of the copolymer to modify the interface. As most polymers which are not block or alternating are termed "random", this differentiation may have an effect on experimental studies of random copolymers as compatibilizers in polymer blends.