Canine periodontal disease is a highly prevalent chronic inflammatory condition with a multifactorial etiology, influenced by host factors and complex subgingival bacterial communities; however, evidence from populations in underrepresented regions remains limited. The objective of this study was to evaluate the association between host factors (age, diet, and cranial morphology) and the presence and severity of periodontal disease, as well as to characterize the subgingival bacterial profile using culture-based methods in an urban clinical population in Ecuador. A cross-sectional, analytical, observational study was conducted on 100 dogs treated at veterinary clinics in Loja. Periodontal status was classified according to AVDC criteria, defining the outcomes as the presence of periodontal disease (stages 1–4 vs. 0) and advanced periodontitis (stages 2–4 vs. 0–1). Subgingival samples were collected using sterile paper points and processed under aerobic and anaerobic conditions, with analyses performed individually. Periodontal disease was present in 68.0% of dogs, with 37.0% in advanced stages. Age was the only factor independently associated with both the presence (OR = 1.18; 95% CI: 1.02–1.36; p = 0.021) and severity (OR = 1.22; 95% CI: 1.05–1.41; p = 0.009), while diet, sex, and cranial morphology showed no significant associations (p > 0.05). The bacterial profile was polymicrobial (3.86 positive isolates per individual), and no taxon showed a significant association after FDR correction. Taken together, these results support a multifactorial and polymicrobial model, highlighting age as the main associated factor and emphasizing the need for molecular approaches in future studies.