The sustainability of NGO initiatives has become a criterion by which to judge the success of programming. This study explores the conditions needed in order to achieve sustainable change by focusing on a sector that has recently experienced this shift towards more sustainable, interdisciplinary programming: that of working equid (animal welfare) NGOs. Semi-structured, in-depth interviews with 32 NGO staff working for 8 different animal welfare NGOs across 13 countries were conducted. These interviews covered potential barriers and avenues to success in producing sustainable working animal welfare improvements. Thematic analysis revealed consistent themes across contexts and NGOs. Approaches perceived as creating sustainable outcomes were ones that tailored initiatives to local contexts, focused on changing human behaviour, worked with key community contacts, built capacity in local infrastructure, combined approaches, and had comprehensive exit strategies. Barriers to sustainability included lack of continuity, short funding cycles and unpredictable external factors. Consideration of these conditions for designing effective future initiatives is recommended across the wider not-for-profit sector.