Booking.com, eBay, or Uber are all multi-sided plattforms (MSPs) as they facilitate transactions between two or more distinct customer groups. Due to the indirect network effects that arise in markets with MSPs, such markets gravitate towards monopoly outcomes (van Alstyne et al., 2015) and display high barriers to entry once a MSP has successfully been established (Eisenmann et al., 2006). These outcomes render MSPs attractrive entrepreneurial opportunities. Even though start-ups are clearly prevalent in the field of MSPs, it has not yet been examined why or under which conditions start-ups are better placed than incumbents to pursue MSPs. This study aims to address this gap in three ways: Firstly, we identify contextual factors that put start-ups structurally in a better or worse position than incumbents. Secondly, we identify factors and mechanisms that influence the strength of the impact that these contextual factors have on the relative competitive positioning. Finally, we derive steps players can take to improve their relative competitive positioning.