Post-traumatic stress disorder (PTSD) is an often-debilitating and chronic disorder that can develop following exposure to a trauma like a natural or man-made disaster (e.g., hurricane, airplane crash). About 60.7% of men and 51.2% of women in the US general population experience a lifetime trauma. A minority develop PTSD—7–8% in the US general population, and much higher in the military (23% among post-9/11 veterans). PTSD is associated with severe impairments in occupational, social, and family functioning, and with increased odds of emotional and substance disorders. First-line treatments (pharmacotherapy; [mostly exposure-based] psychotherapy) are effective yet suboptimal, leading to a quest for helpful non-exposure-based complementary and alternative treatments that provide long-term care and less stigma. Popular options are canine-assisted interventions (CAIs): emotional support, therapy, and service dogs. Lack of clarity regarding which modality is most efficacious for PTSD impedes policy changes to make CAIs more accessible. We provide a critical evaluation of current evidence regarding the efficacy of each CAI modality for PTSD. Although most evidence endorses service dogs, other canine-assisted modalities might be optimal in specific circumstances. Considerable challenges (e.g., lack of standardized intervention and dog certification protocols; insufficient randomized controlled trials) hinder the incorporation of CAIs into PTSD treatment.