Background: Cannabis is the most widely used illicit substance, and multiple treatment options and avenues exist for managing its use. There has been an increase in the development of clinical practice guidelines (CPGs) to improve standards of care in this area, many of which are disseminated online. However, little is known about the quality and accessibility of these online CPGs. Objective: The purpose of study 1 was to determine the extent to which cannabis-related CPGs disseminated online adhere to established methodological standards. The purpose of study 2 was to determine if treatment providers are familiar with these guidelines and to assess their perceived quality of these guidelines. Methods: Study 1 involved a systematic search using the Google Scholar search engine and the National Drugs Sector Information Service (NDSIS) website of the Alcohol and Other Drugs Council of Australia (ADCA) to identify CPGs disseminated online. To be included in the current study, CPGs needed to be free of charge and provide guidance on psychological interventions for reducing cannabis use. Four trained reviewers independently assessed the quality of the 7 identified guidelines using the Appraisal of Guidelines for Research and Evaluation (AGREE II) tool. Study 2 assessed 166 Australian cannabis-use treatment providers' (mean age = 45.47 years, SD 12.14) familiarity with and opinions of these 7 guidelines using an online survey. Treatment providers were recruited using online advertisements that directed volunteers to a link to complete the survey, which was posted online for 6 months (January to June 2012). Primary study outcomes included quality scores and rates of guideline familiarity, guideline use, and discovery methods. Results: Based on the AGREE II, the quality of CPGs varied considerably. Across different reporting domains, adherence to methodological standards ranged from 0% to 92%. Quality was lowest in the domains of rigor of development (50%), applicability (46%), and editorial independence (30%). Although examination of AGREE II domain scores demonstrated that the quality of the 7 guidelines could be divided into 3 categories (high quality, acceptable to low quality, and very low quality), review of treatment providers' quality perceptions indicated all guidelines fell into 1 category (acceptable quality). Based on treatment providers' familiarity with and usage rates of the CPGs, a combination of peer/colleagues, senior professionals, workshops, and Internet dissemination was deemed to be most effective for promoting cannabis use CPGs. Lack of time, guideline length, conflicts with theoretical orientation, and prior content knowledge were identified as barriers to guideline uptake. Conclusions: Developers of CPGs should improve their reporting of development processes, conflicts of interest, and CPGs' applicability to practice, while remaining cognizant that long guidelines may deter implementation. Treatment providers need to be aware that the quality of cannabis-related CPGs varies substantially.