Homeless people with cocaine use disorder have multiple comorbidities and costly service needs. This study examined service costs associated with cocaine use and substance service use in substance, psychiatric, and medical service sectors. 127 homeless participants with cocaine use disorder were interviewed annually. Self-report and agency-report service use and cost data were combined. Pairwise comparisons were made with cocaine abstinence and substance service use in relation to mean and yearly proportional service costs in 3 service sectors. Among substance service users, achievement of abstinence was not associated with decreased substance service costs. Cocaine abstinence was associated with proportional reduction of substance service costs over time. Substance service use was associated with proportional reduction of psychiatric service costs over time among the abstinent subgroup. Conversely, substance service use was associated with continuing higher medical service expenditures in the abstinent subgroup and higher psychiatric service expenditures in those not abstinent. Homeless individuals who achieved cocaine abstinence after using substance services had decreased substance service expenditures. Individuals with continued substance service use had greater medical and psychiatric service costs. Policy based on maximizing benefits while minimizing costs appears insufficiently complex to incorporate the multiple needs and associated with costs of treating homeless populations.