We examine the influence of multinationality and business group diversification on firm performance. Further, we examine how their interaction varies between service and manufacturing firms. We assess these relations in three Latin American countries using a sample of 103 firms over the period from 2000 to 2007. We found that there is a limit to the positive effects of business group diversification and that business group diversification effectively moderates the multinationality-performance (M-P) relationship. Our results also suggest that diversified business groups have a stronger positive influence on the M-P relationship for service firms compared to manufacturing firms.