PurposeTo empirically study the determinant factors of adopting work–life balance measures at the firm level.Design/methodology/approachAfter reviewing the main theories that explain work–life balance practices, IBEX-35 Spanish companies during 2015–2019 are studied to see whether the firm sector, the presence of female employees, qualified personnel, a company agreement and an equality plan determine these types of practices.FindingsThe results indicate a negative relationship between the firm activity sector and adopting work–life balance practices. Industrial companies offer fewer work–life balance measures than service companies. A company agreement implies more extensive adoption of work-life practices. Older companies are characterized by greater adoption of work-life practices, in contrast to their level of profitability that is associated negatively with these practices.Practical implicationsSince it is difficult for industrial companies to change their idiosyncrasies, it is necessary to incorporate other measures that promote work–life balance, such as timetable flexibility. Companies and policymakers should promote the advantages of a company agreement to contribute to the implementation of work–life balance practices.Originality/valueThe empirical evidence is scarce, especially in Spain and at the company level, given that most previous studies have focused on workers and the Anglo-Saxon sphere. Given the growing interest in this topic in the business world, the authors intend to contribute to this scarce literature by incorporating variables considered in previous studies, as well as other more innovative ones (agreement, equality plan) in a single model through a longitudinal study.