OBJECTIVES:  To evaluate incremental expenditures associated with recurrence of diverticulitis and identify the primary driver of the incremental total expenditure. METHODS:  We conducted a retrospective cohort study on the Kaiser Permanente Southern California Health Plan adults (18+ years) who had acute diverticulitis (incident cases) during 01/01/2007 to 12/31/2011. We identified medical expenditures (2016 USD) associated with inpatient (ip_exp) including emergency department, and outpatient (op_exp) visits during the one year period after the index date for patients without recurrence and one year after the recurrence date for those who had recurrence within one year of the index date. Total expenditure (tot_exp) was the sum of op_exp and ip_exp. A generalized linear model with log link and gamma distribution was specified which adjusted for socio-demographics, insurance, Elixhauser comorbidity, clinical complications at presentation and dummy variable identifying recurrence. To estimate ip_exp, we specified a two part model. RESULTS:  We identified 30,715 incident cases of whom 14% had a recurrence within a year of their index date. The average adjusted tot_exp was $8,325 (95% CI $8,172 to $8,478) for those without recurrence while it was $11,932 ($11,389 to $12,474) in those who experienced a recurrence. The average adjusted op_exp was $3,559 ($3,516 to $3,601) while ip_exp was $4,776 ($4,644 to $4,908) amongst those without recurrence. For those with recurrence, the estimates for op_exp and ip_exp were $4,335 ($4,208 to $4,463) and $7,380 ($6,931 to $7,830) respectively. The incremental difference in tot_exp was $2,911 ($2,468 to $3,355) higher in those who experienced a recurrence and this difference was predominantly driven by ip_exp $2,056 ($1,703 to $2,409). The incremental difference in op_exp was $685 ($568 to $802) higher in those who had recurrence. CONCLUSIONS:  The recurrence of diverticulitis was associated with significantly higher total expenditure that was predominantly related to increased hospitalization and emergency department visits.