This research investigated whether people who fear being single have a more difficult time letting go of ex‐partners following a romantic breakup. Data were collected in a cross‐sectional study (N = 209, 64% women, Mage = 30 years old) as well as a 1‐month daily experience study of individuals who just went through a romantic breakup (N = 117, 44% women, Mage = 27 years old). Findings from both studies revealed that those with stronger fear of being single (Spielmann et al., 2013) reported greater longing for their ex‐partners. Pre‐ to post‐breakup analyses revealed that fear of being single increased after a breakup, regardless of who initiated the breakup. Within‐day analyses revealed that longing for an ex‐partner and attempts to renew the relationship were greater on days with stronger fear of being single. Lagged‐day analyses provided support for the conclusion that fear of being single increased longing and renewal attempts over time, but longing and renewal attempts did not influence fear of being single. These findings suggest that fear of being single is a particularly useful construct for understanding the romantic detachment process.