This paper examines the effects of internal (or regional) vs. external (inter-regional) integration and of trade vs. financial integration on regional business cycle synchronization in Asia. The empirical results show the following: (1) similar and strong common external linkages have significant positive effects on regional business cycle synchronization; (2) after controlling for external linkages, internal trade integration has a positive effect on regional business cycle synchronization but internal financial integration has a negative effect; and (3) the measures of external linkages, particularly the measure of external financial linkages, are more important than those of internal linkages in explaining regional business cycle co-movements.