The widespread use of the term “foster fail” in animal rescue suggests that it happens often, but no research has explored the prevalence of volunteers adopting their foster animals or whether the phenomenon is really a “failure”. This survey-based study focused on the following questions: 1. How common are foster fails among volunteers on shelter and rescue lists and why do they occur? 2. What types of volunteers are most likely to adopt their foster animals? 3. Do different attachment styles to pets affect foster adoption? 4. Is the adoption of foster animals a way to deal with the potential grief of letting them go to adoption? 5. What are the impacts of foster fails on animal shelters in terms of longevity of volunteers and satisfaction with the volunteer experience? Data were collected through surveys of foster volunteers. Two nonprofit organizations, the Pedigree Foundation and Shelter Animals Count, distributed information about the survey and shelter directors distributed the survey link to their population of foster volunteers. Nine hundred and forty-seven individuals responded. To address the research questions, frequency, correlation, and regression analyses were employed. A total of 38% of volunteers had not adopted a foster in the past ten years, and another 38% had adopted one or two; 90 (11%) and 103 (13%) had adopted three to four or more than four, respectively. Volunteers that had significantly higher numbers of foster fails were those that were older (r = 0.22, p < 0.001), retired (chi-squared = 9.05, p = 0.029), lower on educational attainment (r = −0.13, p < 0.001), female with their own cats (r = 0.16, p < 0.001), and part of a fostering family (r = 0.08, p = 0.043). Volunteers that expressed higher levels of both people-substituting (r = 0.16, p = 0.003) and general (r = 0.13, p = 0.017) attachment to their fosters were more likely to adopt them, as were those that more frequently fostered animals with special medical or behavioral needs (r = 0.25, p < 0.001). Volunteers that had longer tenures (r = 0.43, p < 0.001), fostered more frequently (r = 0.24, p < 0.001), and reported greater resilience (r = 0.10, p = 0.009) had adopted significantly more animals. Finally, there was a significant and positive relationship between satisfaction with fostering and adopting more foster animals (r = 0.16, p < 0.001). The findings indicated that instead of being a “failure,” foster adoptions can be a positive force for the animal in question, their adopters, and shelters and rescues because they have more resilient, satisfied, and active volunteers.