Crowdsourcing of inventive activities is a particular form of crowdsourcing that helps firms to innovate by involving dispersed individuals to exploit “crowd wisdom”. In this context, the greater the number of contributions, the greater the possibility to gather extremely valuable ideas to produce innovative products and services. While monetary and social rewards can be an effective means to boost contributors’ extrinsic and intrinsic motivations to contribute, a theoretical understanding and empirical evidence of their effects are lacking. This paper focused on the crowdsourcing of inventive activities, initiated by listed companies worldwide, from 2007 to 2014. Our findings shed light on the influence of monetary and social rewards on the number of ideas collected. In particular, we analyzed the impact on the number of contributions brought about by monetary rewards and noted a positive influence related to its presence and also a negative effect related to the amount of the compensation. Moreover, we have demonstrated how the presence of a social cause is beneficial to the number of contributions. Consequently, we contribute to a scholarly understanding of the crowdsourcing phenomenon and we have provided guidance to managers seeking to initiate crowdsourcing campaigns.