<i>Background:</i> Among older persons with chronic somatic diseases, depression often remains unrecognized and untreated in primary care. The Depression in Elderly with Long-Term Afflictions (DELTA) study aimed to evaluate the effectiveness of a nurse-led minimal psychological intervention (MPI) in chronically ill elderly persons with depression. <i>Methods:</i> A randomized controlled trial was conducted, comparing the MPI with usual care in 361 primary care patients. Four nurses had an average of 4 sessions with the intervention patients, each lasting 1 h, over a maximum period of 3 months. Patients were aged 60 years and older, had a minor depression or mild-to-moderate major depression, and either had type II diabetes or chronic obstructive pulmonary disease. <i>Results:</i> Nine months after the intervention, patients receiving the MPI had significantly fewer depressive symptoms; the intervention patients were also more likely than usual-care controls to show a ≧50% reduction in depressive symptoms relative to baseline values. At 9 months, diabetic MPI patients had a better quality of life than diabetic controls. <i>Conclusions:</i> The nurse-led MPI appears to be a feasible and moderately effective method of managing minor-to-moderate depression in chronically ill elderly persons. However, we cannot rule out attention-placebo effects, and the disappointing finding of a recent economic evaluation showing only a 63% chance of the MPI being cost-effective. From a clinical point of view, however, it is of interest to further evaluate adaptations of the MPI, with a stronger emphasis on detection, watchful waiting and mental health problems in general.