AB Aims: To review the transparency of reports of behavioral interventions for pathological gambling and other gambling-related disorders. Methods: We used the Transparent Reporting of Evaluations with Nonrandomized Designs (TREND) Statement to develop the 59-question Adapted TREND Questionnaire (ATQ). Each ATQ question corresponds to a transparency guideline and asks how clearly a study reports its objectives, research design, analytical methods and conclusions. A subset of 23 ATQ questions is considered particularly important. We searched PubMed, PsychINFO and Web of Science to identify experimental evaluations published between 2000 and 2011 aiming to reduce problem gambling behaviors or decrease problems caused by gambling. Twenty-six English-language reports met the inclusion criteria and were reviewed by three abstractors using the ATQ. Results: The average report adhered to 38.4 (65.1%) of the 59 ATQ transparency guidelines. Each of the 59 ATQ questions received positive responses from an average of 16.9 (63.8%) of the reports. The subset of 23 particularly relevant questions received an average of 15.3 (66.5%) positive responses. Thirty-two of 59 (54%) ATQ questions were answered positively by 75% or more of the study reports, while 12 (20.3%) received positive responses by 25% or fewer. Publication year did not affect these findings. Conclusions: Gambling intervention reports need to improve their transparency by adhering to currently neglected and particularly relevant guidelines. Among them are recommendations for comparing study participants who are lost to follow-up and those who are retained, comparing study participants with the target population, describing methods used to minimize potential bias due to group assignment, and reporting adverse events or unintended effects.