Although close relationships are often characterized by openness and disclosure, in the present research, we propose that there are times when individuals choose not to tell close others about their consumer behavior, keeping it a secret. For example, one partner may eat a candy bar on the way home from work, hide a package that was delivered to the house, or hire a cleaning service and not tell the other partner. We theorize that this type of consumer behavior is both common and mundane. That is, the consumption itself is minor—and has likely been done with the partner's knowledge in the past—but is being intentionally kept from the partner. We further investigate whether such behavior has downstream effects on the relationship, despite its mundaneness. Five studies support our conceptualization of secret consumer behaviors in close relationships and illustrate one consequence: guilt from secret consumption leads to greater relationship investment. This research explores a common, yet understudied, area of consumer behavior and highlights areas for future research. Thus, we contribute to the literature by being the first work to examine emotional, behavioral, and relational aspects of secret consumer behavior.