ABSTRACT The present study theoretically examines the effects of free technology sharing by a monopolistic final-goods firm with other final-goods firms. I consider two cases: first, where there exists one final-goods firm in the final-goods market and second, where there exist two final-goods firms in the final-goods market. Given the free entry of firms into the differentiated intermediate-goods market, the results show that when another firm enters the final-goods market and transforms it into a two-firm oligopoly, cost efficiency improves because of an increase in the number of intermediate-goods firms. Furthermore, there is a possibility that the incumbent firm’s profits increase not only for a two-firm oligopoly, but also for an oligopoly with three or more firms. Thus, this study concludes that free technology sharing can improve incumbent firms’ profits. When the impact of an increased number of firms entering the intermediate-goods sector on the final good’s unit cost is high, free technology sharing benefits incumbent firms’ profits. While some prior studies show the potential for firms to increase their profits through licencing and the provision of technology, this study considers that technology is shared free of charge in an economy where the number of differentiated intermediate-goods firms is endogenously determined.