Abstract Background The majority of the world’s perinatal deaths occur in low- and middle-income countries. A substantial proportion occurs intrapartum and is avoidable with better care. At a low-resource tertiary hospital, this study assessed the quality of intrapartum care and adherence to locally-tailored clinical guidelines. Methods A non-participatory, structured, direct observation study was held at Mnazi Mmoja Hospital, Zanzibar, Tanzania, between October and November 2016. Women in active labour were followed and structure, processes of labour care and outcomes of care systematically recorded. Descriptive analyses were performed on the labour observations and compared to local guidelines and supplemented by qualitative findings. A Poisson regression analysis assessed factors affecting foetal heart rate monitoring (FHRM) guidelines adherence. Results 161 labouring women were observed. The nurse/midwife-to-labouring-women ratio of 1:4, resulted in doctors providing a significant part of intrapartum monitoring. Care during labour and two-thirds of deliveries was provided in a one-room labour ward with shared beds. Screening for privacy and communication of examination findings were done in 50 and 34%, respectively. For the majority, there was delayed recognition of labour progress and insufficient support in second stage of labour. While FHRM was generally performed suboptimally with a median interval of 105 (interquartile range 57–160) minutes, occurrence of an intrapartum risk event (non-reassuring FHR, oxytocin use or poor progress) increased assessment frequency significantly (rate ratio 1.32 (CI 1.09–1.58)). Conclusions Neither international nor locally-adapted standards of intrapartum routine care were optimally achieved. This was most likely due to a grossly inadequate capacity of birth attendants; without whom innovative interventions at birth are unlikely to succeed. This calls for international and local stakeholders to address the root causes of unsafe intrafacility care in low-resource settings, including the number of skilled birth attendants required for safe and respectful births.