Background. South Africa (SA) experiences vaccine-preventable disease outbreaks despite officially reporting high administrative fully immunised under-1-year-old coverage (FIC) figures. Objective. To investigate immunisation coverage and reasons for missed vaccinations in Tshwane Region 5 in Gauteng province, SA, in 2017. Methods. A household survey, based on a World Health Organization protocol, was conducted among consenting caregivers of children aged 12-23 months who had Road to Health cards (RtHC). RtH cards were checked and photographed, and reasons were recorded for missed vaccinations. Epi Info 7 was used for descriptive statistical analysis. Results. Eligible children resided in 327 of 8 060 houses visited, with 84.4% (n=276/327) of caregivers consenting to participate. Vaccination coverage ranged from 99.6% (n=275/276) for the oral polio vaccine at birth to 87.3% (n=241/276) for the third dose of the pneumococcal conjugate vaccine (PCV3). Of the children who received PCV3, 24 had missed earlier vaccinations, resulting in a FIC rate of 78.6% (n=217/276). Overall, 123 vaccinations were missed by 59 children, with reasons related to health facility obstacles (34.1%; n=42/123) and lack of information (26.8%; n=33/123) being the largest contributors. Conclusion. The FIC rate of 78.6% can realistically be improved, as most missed vaccinations are due to modifiable healthcare facility obstacles, including poor communication. Suggested solutions include providing accredited programmes for empowering vaccinators to effectively communicate with their clients and manage vaccination logistics, and extending clinic hours to early evenings and weekends.