Informal care is today the form of support most commonly used in Spain by those who need help in order to carry out basic daily activities. The potential labour opportunity costs incurred by Spanish informal carers have not as yet been quantified. In this paper we use the Spanish subsample of the European Community Household Panel (1994–2001) to estimate an econometric model which we exploit to examine the effects of various types of informal care on labour market outcomes. Our results reveal the existence of non-negligible costs in terms of foregone employment for carers who live with the dependent person and/or provide more than 28 h of care/week. We also find that providing care for more than a year has negative effects on employment. Nonetheless, there seems to be no contemporaneous employment effects associated to either starting or ending an episode of care.