BACKGROUND: It is important to know the decay of knowledge, skills, and confidence over time to provide evidence-based guidance on timing of follow-up training. Studies addressing retention of simulation-based education reveal mixed results. The aim of this study was to measure the level of knowledge, skills, and confidence before, immediately after, and nine months after simulation-based training in obstetric care in order to understand the impact of training on these components. METHODS: An educational intervention study was carried out in 2012 in a rural referral hospital in Northern Tanzania. Eighty-nine healthcare workers of different cadres were trained in "Helping Mothers Survive Bleeding After Birth", which addresses basic delivery skills including active management of third stage of labour and management of postpartum haemorrhage (PPH). Knowledge, skills, and confidence were tested before, immediately after, and nine months after training amongst 38 healthcare workers. Knowledge was tested by completing a written 26-item multiple-choice questionnaire. Skills were tested in two simulated scenarios "basic delivery" and "management of PPH". Confidence in active management of third stage of labour, management of PPH, determination of completeness of the placenta, bimanual uterine compression, and accessing advanced care was self-assessed using a written 5-item questionnaire. RESULTS: Mean knowledge scores increased immediately after training from 70 % to 77 %, but decreased close to pre-training levels (72 %) at nine-month follow-up (p = 0.386) (all p-levels are compared to pre-training). The mean score in basic delivery skills increased after training from 43 % to 51 %, and was 49 % after nine months (p = 0.165). Mean scores of management of PPH increased from 39 % to 51 % and were sustained at 50 % at nine months (p = 0.003). Bimanual uterine compression skills increased from 19 % before, to 43 % immediately after, to 48 % nine months after training (p = 0.000). Confidence increased immediately after training, and was largely retained at nine-month follow-up. CONCLUSIONS: Training resulted in an immediate increase in knowledge, skills, and confidence. While knowledge and simulated basic delivery skills decayed after nine months, confidence and simulated obstetric emergency skills were largely retained. These findings indicate a need for continuation of training. Future research should focus on the frequency and dosage of follow-up training.