Mental health issues such as depression or anxiety and alcohol or other drug (AOD) problems often remain undiagnosed and untreated despite their prevalence in the community. This paper reports on the implementation and evaluation of an AOD and depression/anxiety screening programme within two Community Health Services (CHS) in Australia. Study 1 examined results from 5 weeks of screening (March–April 2008) using the Patient Health Questionnaire (two- and nine-item, Kroenke et al. 2001, 2003), the Conjoint Screen for Alcohol and other Drug Problems (Brown et al. 2001) and the Alcohol, Smoking and Substance Involvement Screening Test (Humeniuk & Ali 2006). Of the 55 clients screened, 33% were at risk of depression or anxiety, 22% reporting moderate-severe depression. Thirteen per cent were at risk of substance use disorders. A substantial proportion of at-risk clients were not currently accessing help for these issues from the CHS and therefore screening can facilitate identification and treatment referral. However, the majority of eligible clients were not screened, limiting screening reach. A second study evaluated the screening implementation from a process perspective via thematic analysis of focus group data from six managers and 14 intake/assessment workers (April 2008). This showed that when screening occurred, it facilitated opportunities for education and intervention with at-risk clients, although cultural mores, privacy concerns and shame/stigma could affect accuracy of screen scores at times. Importantly, the evaluation revealed that most decisions not to screen were made by workers, not by clients. Reasons for non-screening related to worker discomfort in asking sensitive questions and/or managing client distress, and a reluctance to spend long periods of time screening in time-pressured environments. The evaluation suggested that these problems could be resolved by splitting screening responsibilities, enhancing worker training and expanding follow-up screening. Findings will inform any community-based health system considering introducing screening.