The aim of the present study was to investigate the relationship between treatment delay and excessive substance use. A total of 151 bipolar disorder (BD) I and II patients were consecutively recruited from in- and outpatient psychiatric units, and categorized as primary or secondary BD (without or with antecedent excessive substance use). Predictors of treatment delay among all patients, and predictors of subsequent excessive substance use among primary BD patients, were investigated with logistic regression analyses. The median treatment delay was 2.0 years (IQR 14.0). The risk of long treatment delays was increased in patients with BD II disorder, no lifetime psychosis, a higher age at first contact with specialized psychiatric services, primary BD, and excessive substance use. In primary BD, the risk for developing excessive substance use was increased in males, in patients with shorter education and longer treatment delays. Patients with antecedent excessive substance use had reduced risk of long treatment delays. The risk of developing excessive substance use after BD onset increased with longer treatment delays.