Background: While failure in social marketing practice represents an emerging research agenda, the discipline has not yet considered this concept systematically or cohesively. This lack of a clear conceptualization of failure in social marketing to aid practice thus presents a significant research gap. Focus: This study aimed to conceptualize failures in social marketing practice. Methods: A qualitative survey was conducted using purposive sampling to solicit expert views of well-established social marketing academics and practitioners. Participants were asked to discuss failures in social marketing practice based on their experience in the field. A total of 49 participants provided their input to the survey. Thematic analysis was used to develop four themes addressing the research question. Importance: It is widely acknowledged that reflecting and learning from past failures to promote future best practices is desirable for any discipline. As an empirically based social change discipline, social marketing would benefit from the elevation of failure within its broader research agenda. Results: Four themes were identified: (1) Failures occur when the target behaviors are not achieved, (2) Tactics used to measure failures, (3) Process failure, and (4) Failures either not measured or reframed as lessons learned. A conceptual framework was created to characterize the nature of failures in social marketing practice, representing a feedback loop deemed problematic for the discipline. Recommendations: We call for social marketers to explicitly acknowledge and address failures when describing and reporting on their work and project outcomes. Efforts should be made to adopt a reflexive stance and examine and address internal and external factors affecting the program’s failures.