This article explores the conditions under which unions achieve inclusive outcomes for nonstandard workers in their collective agreements. Using fsQCA, it compares 52 collective agreements signed in Portugal between 2003 and 2019. Additionally, it reports on three short case studies. Results show that the unions’ potential to mobilize resources in favour of outsiders is crucial and is due to either high union density or unions’ class-oriented ideology. However, although a high potential to mobilize resources is necessary, it is not sufficient for pro-outsider provisions in collective agreements. In a context of growing liberalization of industrial relations, unions only include these clauses in their collective agreements in one of the following circumstances: (i) the combination of high union density and sectoral growth, (ii) the combination of a class-oriented union signing the agreement and low employer density and (iii) the combination of high union density and a class-oriented union signing the agreement.

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• Economics and Business - Social Sciences