In this paper we estimate the causal effect of providing “intensive” informal care to elderly parents on labour market participation decisions for European women who are themselves approaching retirement. In particular, we consider the frequency or intensity of this help and we focus on informal care provided in a daily or weekly basis. We use two different but comparable samples drawn from the Survey of Health, Ageing and Retirement in Europe (SHARE) that provide complementary detailed information about daughters and parents. We obtain evidence about this question for two groups of European countries that strongly differ in terms of informal caregiving intensity within the immediate family and the use of formal care: the northern countries (Sweden, Denmark and The Netherlands), and the southern countries (Spain, Italy and Greece). The results show that the estimated effect of providing “intensive” informal care to elderly parents on the probability of labour participation is negative and large for both groups of countries. Furthermore, a substantially stronger effect is found when the “intensive” caregiving variable is treated as endogenous in the labour participation equation. This shows that the potential opportunity costs in terms of (reduced) employment associated with the provision of informal care by women are seriously underestimated under the exogeneity assumption of the caregiving regressor.