The dynamics of protection in the context of socio-technical niches have remained underresearched. In this paper we conceptualise the process of policy learning in the context of transitions. We show that a variety of actors inside and outside a technological niche have to learn about the implications and effects of regulations aimed at protection of niches. We analyse this process of policy learning in two cases: high-need drugs and electric vehicles. We conclude that both regulators and the regulated need to learn about the width and depth of protection measures, their duration, the specific set of tools used, and their legitimisation. A crucial issue of implementing protective regulation is the question on what level of aggregation protection measures need to be applied. Learning is often part of the negotiation process between the protector and the protected, but in many cases learning only takes place after policies have been implemented.