Euthanasia in small-animal practice is often framed as a technical endpoint; this study demonstrates it is fundamentally relational and context-dependent. Drawing on 29 qualitative interviews with Istanbul-based small-animal veterinarians (conducted in Turkish, July 2024–April 2025), I examine how ethical reasoning, emotional labor, and institutional conditions shape life-ending decisions for two canine populations: companion animals and unowned street dogs. Reflexive thematic analysis, informed by constructivist grounded theory, reveals that euthanasia for companion dogs typically unfolds through shared deliberation with owners, anticipatory grief work, and post-death rituals—distributing moral responsibility across human actors. By contrast, street-dog cases commonly occur without legal guardianship, with ambiguous authorization, compressed timelines, and scarce aftercare, concentrating ethical burden and moral residue on veterinarians themselves. Six cross-cutting themes structure the findings: shouldering responsibility in the absence of guardians; ethical strain under contested indications; the decisive role of relational presence; the unequal weight of municipally routed street-dog euthanasia; practices of witnessing that seek dignity at the end of life; and the ethics of time as a finite clinical resource. The study advances empirical veterinary ethics by reframing euthanasia as work performed within—and often against—fragile urban care infrastructures. Implications include training for adverse-euthanasia scenarios, municipal protocols for unowned animals (authorization lines, funded aftercare), and clinic-level supports (sedation-first SOPs, rotation, debriefing). Recognizing how context redistributes responsibility clarifies both the possibilities and limits of “humane” endings in urban practice.