This article examines union strategies towards the twin digital and green transitions, comparing the German and Belgian automotive industries. The drive towards net-zero and more digital economies is manifested through the move from fossil fuel-powered cars to electric cars, engendering a reorganisation of production, work and employment among car manufacturers. We identified two strategic union response patterns. While German unions are developing proactive strategies and proposals to influence and shape the ongoing transition of the automotive industry, Belgian unions are more passive, reacting primarily to management proposals and focusing narrowly on employment and working conditions without a broader strategy on how to influence the transformation of the automotive industry. We explain the observed cross-national differences by two factors: the importance of national institutions, i.e., the varying integration of labour into management decision-making, and the role of union knowledge regimes. The latter refers to internal union organisations and structures such as research departments, research institutes and foundations tasked with providing own research and funding external research on change topics from a union perspective, publishing studies and developing programmatic agendas, and disseminating the knowledge to union members through training, workshops and conferences.