We analyze empirically whether trade and financial linkages between two countries increase the synchronization of their business cycles directly or indirectly. In a system of equations, we use a newly processed database on the bilateral linkages of a small open economy, namely Spain. We prefer this to the generally used US data, to avoid other channels of influence of such a large economy affecting the results. We find that both trade or financial linkages only foster synchronization of business cycles indirectly, by increasing the similarity of economic structure between countries, which itself induces more similar output movements. This result suggests that sectoral shocks, rather than intra-industry shocks, have prevailed in the last 15 years. The net effects of both trade and financial linkages on business cycle synchronization are statistically significant, but very small in economic terms. Common macroeconomic policies, instead, are much more important determinants of output co-movements.