We examine the effect of joining the European Union on individual life satisfaction in Bulgaria and Romania in the context of the 2007 EU enlargement. Although EU membership is among the most important events in Bulgaria and Romania's modern histories, there is no evidence on how it affected the subjective well-being of ordinary people in the two countries. Using a difference-in-differences strategy and Eurobarometer data, we provide the first evidence that joining the EU increased average life satisfaction in Bulgaria and had a positive but statistically insignificant effect in Romania. One explanation is that trust towards the EU increased only in Bulgaria but not in Romania after both countries joined in 2007. Furthermore, Romania's political war of 2007 may have mired the country's positive life satisfaction experiences related to EU membership. We also show that the younger, the employed, and those with a high-school education were the winners from EU integration. Our results are robust to two placebo tests, in which we use two fake entry dates to the EU, and to an estimation using bootstrapped standard errors. Our findings have implications for EU integration policy and future enlargements.