Background: Brucellosis in dogs caused by Brucella suis is an emerging zoonotic disease. Objectives: To document clinical characteristics, serology, microbiology, and clinical response to treatment in B. suis-seropositive dogs. Animals: Longitudinal study of 27 privately-owned dogs. Dogs that tested positive by serology, culture, or real-time polymerase chain reaction (qPCR) were included in the study. Methods: Clinical (physical examination and imaging) and laboratory (serology, hematology, serum biochemistry, and qPCR or culture) assessments were made at baseline and after approximately 3, 6, 12, and 18 months. Results: Dogs were followed for 10 895 dog days, with 17/27 dogs completing the 18-month follow-up. Ten dogs had signs consistent with brucellosis before enrollment (n = 4), at baseline (n = 2) or during follow-up (n = 6), with 2 dogs experiencing relapse of historical signs. Antibody titers persisted for the duration of follow-up in 15/17 dogs (88%). Radiographic (n = 5) and ultrasound (n = 11) findings, of variable clinical relevance, were observed. Brucella DNA and organisms were detected in 3 dogs, all of which had clinical signs, including in the milk of a bitch around the time of whelping. Brucella DNA was not detected in blood (n = 92 samples), urine (n = 80), saliva (n = 95) or preputial swabs (n = 78) at any time during follow-up. Six dogs underwent treatment, all of which achieved clinical remission although remission was not reflected by decreasing antibody titers. Conclusions and Clinical Importance: Most dogs with B. suis infections have subclinical infections. Serology is poorly associated with clinical disease. Excretion of