Depression is among the leading causes of decreased disability-adjusted life years in the world¹ and a serious public health problem.² Older adults with DM experience greater risk for comorbid depression compared to those who do not have DM.³ Having DM increases the risk of subsequent development or recurrence of depression. Conversely, history of depression increases the risk for new onset DM.⁴ As an unwanted co-traveler of DM, undetected, untreated or undertreated depression impinges an individual’s ability to manage their DM successfully, hindering their adherence to treatment regime.⁵ It also undermines the effectiveness of provider-patient communication and decays therapeutic relationships. Thus, in the context of caring for older adults with DM, comorbid depression presents special challenges and opportunities for clinicians. Moreover, recent studies have suggested that co-occurring depression and DM may accelerate cognitive decline, highlighting the importance of treating depression and DM. Several treatment modalities are available, which can be used to treat and manage depression in primary care settings: pharmaceutical, brief psychotherapeutic, behavioral and life style interventions, and combination therapies. An evidence-based health care delivery model is also available for treating depression in primary care settings. In this article, we summarize the clinical presentation of late-life depression, potential mechanisms of comorbidity of depression and DM, importance of depression in the successful management of DM, and available best practice models for depression treatment.