Museums can be restorative environments that promote recovery from directed attention fatigue. The current study investigated the effect of the time spent in a museum on the perception of the museum as restorative environment. A total of 67 participants were randomly assigned to three experimental conditions that differed in how much time participants spent in the museum: 10 min, 45 min, or 110 min. Additionally, we assessed participants' subjective experience of the duration (i.e., too short, ideal, too long). As a baseline for nonrestorative environments, we measured the perceived restorativeness of the museum lobby and compared it with the perceived restorativeness of the museum, rated after the visit. Overall, the museum was perceived as a restorative environment, and this was not significantly modulated by the objective visit duration. However, the subjective appropriateness of the visit duration significantly predicted the perceived restorativeness of the museum. Specifically, participants who perceived their visit as too long rated the restorativeness of the museum as lower compared with participants who perceived the length of their visit as either too short or ideal. Hence, it is the subjective instead of the objective visiting duration that determines the restorativeness of museums. The findings are discussed in the context of attention restoration theory.