Grassroots innovations provide a significant contribution to sustainability transitions. They differ from other innovations as they originate in civil society and are mostly inspired by ideological values. While there is extensive literature on the embeddedness of grassroots innovations at the local scale, there is a lack of systematic analysis in the most prominent processes at supra-local and global scale, including mainstreaming. The mainstreaming of grassroots innovations is often characterized by ideological conflicts between (both grassroots and non-grassroots) actors that can give rise to multiple pathways, corresponding to different interpretations and divergent practices of the same grassroots innovation. This paper investigates two issues that are not considered by the relevant literature: 1) the factors underlying the generation of multiple pathways of the same grassroots innovation; 2) the relationship between the dynamics of each pathway and its outcome. Six agrifood and urban mobility grassroots innovations are considered: Fair Trade, Organic, Veganism, Carsharing, Cycling, Shared Space; their analysis is carried out through longitudinal global scale case studies. The comparison between the case studies put in evidence some recurrent patterns between the dynamics and outcome of grassroots innovation pathways. In particular, the presence of bifurcations resulting in multiple pathways is systematic and is always linked to mainstreaming. In terms of outcomes, a trade-off is observed between the congruence with original values (usually high in non-mainstreaming pathways and low in mainstreaming pathways) and the level of empowerment (usually low in non-mainstreaming pathways and medium-high in mainstreaming pathways). Compared to Big Firms, the involvement of institutions into mainstreaming results in less pronounced trade-offs and greater empowerment.