Objectives: Inappropriate prescription medication use can have significant consequences. Although it is suspected that Aboriginal populations within Canada have high rates of inappropriate use, published information is lacking. To better understand this issue, we studied an Aboriginal population seeking addiction treatment. Methods: We sun-eyed Aboriginal clients who accessed addiction treatment in Calgary, Alberta, for prescription medication use in the previous year, frequency of medication use., and medication source(s), if inappropriately used. Results: Sixty-nine percent of the clients completed the survey (n = 144). Most respondents were aged 31 to 50 years (56%), and 52% were male. Of the respondents, 48% reported that they used prescription medication inappropriately, 8% indicated appropriate use, and the rest indicated no medication use. Sedatives or relaxants were most frequently used inappropriately. Among those who inappropriately used medication, 47% used medication more than 10 times in the previous year. Common sources for those who used medication inappropriately included medication given by a friend or a stranger (52%), medication bought on the street (45%), and medication prescribed by a physician (41%). Age greater than or equal to 30 years was associated with inappropriate use. Sex, residence, and Aboriginal status were not found to be associated with inappropriate use. Conclusion: Inappropriate prescription medication use was a significant problem among an Aboriginal population that sought addiction treatment, and many of these individuals accessed medication from a prescribing physician.