Simple SummaryMillions of cats end up in U.S. animal shelters every year. Cats living in shelters may face several stressors due to social isolation, lack of enrichment, and disturbances in their environment. Although fostering programs for dogs have been well-established in many areas, these programs are extremely rare for cats. The aim of this research was to empirically evaluate outcomes associated with placing shelter cats in a short-term foster environment, when compared with cats that remained in the shelter. Results indicate that cats placed in foster care were not at a disadvantage. Foster cats did not display decreased social behavior, increased fear or aggression, or increased cortisol levels while in the foster home. Therefore, even short-term cat fostering does not appear to be more stressful for cats than staying in the shelter. This work provides empirical evidence that cats can be placed into foster homes, even for short periods of time, when shelter space is limited.Recent research has demonstrated that cats (Felis catus) have greater social potential and flexibility than was previously assumed. However, many traditional cat care practices have been influenced by the misconception that cats are socially aloof. This can result in less support or guidance for cat-focused programs that may promote improved success or welfare. For example, while dog fostering programs—even overnight programs—are considered highly beneficial, with research to back these claims, relatively little research has been dedicated to understanding the potential risks and benefits of cat fostering programs. Therefore, the aim of this study was to empirically evaluate the social, behavioral, and stress response outcomes associated with placing shelter cats in an overnight or short-term foster environment. While neither overnight nor 1-week fostering lead to a statistically significant improvement in human-directed social behavior or stress levels, foster cats also did not display increased fear or aggression in the foster home and did not have higher cortisol levels. Therefore, cat fostering—even short-term fostering—does not appear to be more stressful or problematic for this species than remaining in a shelter. This information could contribute to life-saving efforts by providing empirical evidence that cats can be safely moved into foster homes, even for short durations, when shelter space is limited. More research is needed to evaluate the potential effects of longer-term fostering in cats, as well as cat fostering practices that could lead to greater welfare benefits.