The human-animal bond can lead to a highly positive experience for both the guardian and the animal, nonetheless there is a need to be cognisant of the potential negative aspects this relationship may pose. This scoping review aimed to systematically identify the potential negative guardian aspects associated with pet guardianship and their causative factors, to facilitate a greater understanding and address and minimise these aspects. Through the online databases Scopus, ProQuest and PubMed, a systematic search was conducted, with 6871 sources identified, screened to 76 final sources for inclusion. Numerous potential negative aspects of pet guardianship were identified. The most documented were perceived cost, burden of care and negative aspects of caretaking, followed by grief, negative effects on guardian life satisfaction, and increases in guardian stress, anxiety and/or depression levels. Guardian concern and relinquishment, and disenfranchised guilt about dog parenting were also identified as negative aspects of guardianship. These negative aspects were brought about by various causative factors, such as problem behaviours, caring for a sick or aging pet, the burden of everyday care, and the death of a pet. Whilst integral to the lives of their guardians and providing many positive impacts, the pet guardian relationship is not without challenges. Through further research, particularly regarding the financial constraints that pets may pose for guardians, we can continue to facilitate an overall positive experience for both the guardian and their pet.