Objective: to evaluate the effect of discharge planning conducted by nurses for informal caregivers of dependent people in increasing competence to care and reducing hospital readmissions. Method: a simple, randomized clinical trial conducted with two groups. Ninety-one dyads of informal caregivers-dependent people allocated to the Intervention Group (n=46) and Control Group (n=45) participated. Data collection, carried out in 2021, lasted eight months. The caregivers' outcomes (competence and hospital readmissions) were measured using the COPER-14 instrument at the following moments: pre-/post-intervention; and first, fourth and eighth week after discharge. Results: the informal caregivers' competence for care was 38% (p<0.001) higher in the Intervention Group. Competence was related to the caregiver's previous experience with care (18% higher, p<0.001) and to the experience of readmissions (11% higher, p<0.001). The Intervention Group had more readmissions (24%), whereas the Control Group showed more readmissions within seven days of discharge (13%). Conclusion: the intervention was effective in increasing the competence of informal caregivers of dependent people in the dehospitalization process; however, it did not reduce the number of readmissions. Brazilian Clinical Trials Registry: RBR-5rzmzf.