The burden of heart failure increases over time and is a leading cause of unplanned readmissions worldwide. In addition, its impact has doubled in countries with limited health resources, including Ethiopia. Identifying and preventing the possible contributing factors is crucial to reducing unplanned hospital readmissions and improving clinical outcomes. The study aimed to assess the incidence and predictors of 30-day unplanned readmission among heart failure patients at selected South Wollo general hospitals in 2022. A hospital-based retrospective cohort study design was employed from January 1, 2016, to December 30, 2020. The data was collected from 572 randomly selected medical records using data extraction checklists. Data were entered in Epi-Data version 4.6 and analyzed with Stata version 17. The Kaplan–Meier and log-rank tests were used to estimate and compare the survival failure time. A Cox proportional hazard analysis was used to identify the predictors of readmission. The statistical significance level was declared at a p-value < 0.05 with an adjusted odds ratio and a 95% confidence interval. A total of 151 (26.40%) heart failure patients were readmitted within 30 days of discharge. Among the study participants, 302 (52.8%) were male, and 370 (64.7%) were rural residents. The mean age was 45.8 ± 14.1 SD years. In the multivariate Cox proportional hazards analysis being an age (> 65 years) (AHR: 3.172, 95% CI:.21, 4.55, P = 0.001), rural in residency (AHR: 2.47, 95%CI: 1.44, 4.24, P = 0.001), Asthma or Chronic Obstructive Pulmonary Disease (AHR: 1.62, 95% CI: 1.11, 2.35, P = 0.012), HIV/AIDS (AHR: 1.84, 95%CI: 1.24, 2.75, P = 0.003), Haemoglobin level 8–10.9 g/dL (AHR: 6.20, 95% CI: 3.74, 10.28, P = 0.001), and Mean platelet volume > 9.1 fl (AHR: 2.08, 95% CI: 1.27, 3.40, P = 0.004) were identified as independent predictors of unplanned hospital readmission. The incidence of unplanned hospital readmission was relatively high among heart failure patients. Elderly patients, rural residency, comorbidity, a higher mean platelet volume, and a low hemoglobin level were independent predictors of readmission. Working on these factors will help reduce the hazards of unplanned hospital readmission.