Research summary: This study explores the relationship between business model diversification (BMD) and firm performance from a demand-side perspective. We focus on the addition of a business model with a high degree of demand complementarity, which we refer to as demand-related argue and show that demand-related BMD increases firm performance and is more profitable than demand-unrelated BMD. We also explore external market conditions under which demand-related BMD should lead to greater performance improvements. Our results reveal that demand-related BMD is more profitable in markets with higher demand heterogeneity-as fostered by increases in consumer incomes-and increased technology availability that enables consumers to act on their heterogenous preferences. K E Y W O R D S business model, demand-side perspective, diversification, firm performance, retail sector