The objective of this retrospective study was to determine if a jail diversion program reduced days of incarceration over the year following arrest in a sample of detainees with substance abuse disorders who had been arrested for a minor (misdemeanor) crime (n = 252) compared to a group (n = 95) who were not diverted. Particular attention was paid to comparing those singly diagnosed to those dually diagnosed. Analyses indicated that 1) detainees with substance abuse alone were less likely to be diverted than those with a dual diagnosis; 2) jail diversion reduced incarceration time during the next year; and 3) the effect of diversion differed depending upon the level of criminal charge. Diversion significantly reduced jail time only among those who were arrested for the more serious of the minor offenses that are associated with longer jail sentences.