The field of disability studies has largely overlooked the role of trade unions in the promotion of the rights of workers with disabilities. To address this oversight, this article explores how union activists pursue disability rights and how this cause is situated in their struggle for workers’ rights in Belgium, a country which both has a strong welfare system and gives a predominant role to social partners in industrial relations. It argues that there is a division of work inside unions between representatives at branch level who lobby to increase job opportunities in sheltered workshops and diversity officers at interbranch level who attempt to strengthen equality in the ordinary labour market. Although these two groups do not pursue disability rights in the same way, they share in common a reluctance to mobilise antidiscrimination law because the ideals of equality contradict the routinised practices of employers and of workers’ organisations. Points of interest: 1) In most countries, people with disabilities experience higher unemployment rates than those without a disability. When they work, they are more likely to be found at lower-skilled and part-time positions, as they face discrimination. 2) In Belgium, trade unions are very active in supporting workers’ rights but their attitude towards disability rights is still very poorly documented. 3) Based on interviews with union activists, this study shows that trade unions focus mainly on the development of an adapted work sector, by increasing the number of places in sheltered workshops. 4) Diversity officers working in trade unions aim to combat discrimination in employment but they are reluctant to criticise an employer who do not comply with the law because they fear to harm further negotiation with employers.