The paper analyses the willingness to act as a crowdshipper in the case of a last mile B2C e-commerce for pick up/delivery. Specifically, it focuses on crowdshipping services deployed using the public transport network and considering passengers as crowdshippers already moving for other reasons. In fact, this is the most environmental-friendly type of service one can develop given it avoids performing dedicated trips. The paper uses stated preference to identify the most important features associated with the choice of acting as a crowdshipper and discrete choice models to study the underlying behavior. The implementation case study refers to the city of Rome, Italy, and addresses its metro lines, thus understanding and quantifying the effects of this freight transport strategy for e-commerce in an urban context and providing local policy makers a good knowledge base for its future development.