First-seizure clinics (FSCs) aim to deliver prompt specialist care to patients with new-onset undifferentiated seizure events. To determine whether FSC attendance and time to FSC are associated with subsequent health care utilization and mortality and to investigate factors associated with FSC nonattendance. This was a record-linkage, retrospective, cohort study of patients who booked appointments at 2 FSCs between 2007 and 2018. Patients' records were linked to state-wide administrative databases between 2000 and 2021. The setting comprised the FSCs of 2 major metropolitan public hospitals in Melbourne, Australia, providing national inpatient and outpatient adult epilepsy services. Of patients who booked appointments at the FSCs, those who were successfully linked for analysis were included in the study. Patients who recorded only canceled appointments were excluded from analysis of outcomes. Study data were analyzed from January 2000 to December 2021. FSC attendance. Subsequent all-cause and seizure-related emergency department (ED) presentations and hospital admissions. Of 10 162 patients with appointments at FSCs, 9392 were linked for analysis, with mean (SD) follow-up time 6.9 (2.8) years after FSC referral. A total of 703 patients were excluded. Among 9392 linked patients, 5398 were male (57.5%; mean [SD] age, 59.7 [11.2] years). FSC attendance was associated with reduced subsequent all-cause emergency presentations (adjusted incidence rate ratio [aIRR], 0.72; 95% CI, 0.66-0.79) and all-cause hospitalization (aIRR, 0.81; 95% CI, 0.75-0.88). Those who attended at the first-scheduled appointment, compared with those who attended only a rescheduled, delayed appointment, had reduced subsequent all-cause emergency presentations (aIRR, 0.83; 95% CI, 0.76-0.91), all-cause hospitalization (aIRR, 0.71; 95% CI, 0.65-0.79), seizure-related presentations (aIRR, 0.40; 95% CI, 0.33-0.49), and mortality (hazard ratio, 0.82; 95% CI, 0.69-0.98). Male sex was associated with nonattendance (adjusted relative risk [aRR], 1.12; 95% CI, 1.03-1.22), as were injury at emergency presentation (aRR, 1.12; 95% CI, 1.01-1.24), psychiatric comorbidity (aRR, 1.68; 95% CI, 1.55-1.81), previous seizure-related presentations (aRR, 1.35; 95% CI, 1.22-1.49), and delays (>14 days) between FSC referral and appointment (aRR, 1.35; 95% CI, 1.18-1.54). Hospitalization at referral was associated with reduced nonattendance (aRR, 0.80; 95% CI, 0.72-0.90), as were non-English language preference (aRR, 0.81; 95% CI, 0.69-0.94), distance greater than 6 mi from home to clinic (aRR, 0.85; 95% CI, 0.76-0.95), and physical comorbidity (aRR, 0.80; 95% CI, 0.72-0.89). Results of this cohort study suggest that FSC attendance, particularly early attendance, was associated with reduced rates of subsequent hospital utilization. This knowledge may support adequately resourcing FSCs to improve equitable, timely access. Future study directions include assessing interventions that may support FSC attendance for at-risk groups.