Due to rising global rates of childhood obesity, the World Health Organization (WHO) has recommended the adoption of policies to restrict children's exposure to the advertising of unhealthy foods and beverages. In 2017, the Slovenian government introduced regulations to restrict the advertisement of unhealthy foods and beverages during designated children's television programming. The objective of our study was to assess the impact of these regulations on children's exposure to food advertising, including during children's programmes and at peak viewing times for children. Using a standardised methodology, we investigated a large sample of 6479 food advertisements broadcast during 1652 h of television programming between 2016 and 2018 on the five most popular television channels for children aged 4–9 years. Advertised food products were coded using the WHO Regional Office for Europe Nutrient Profile Model, modified for Slovenia. The average overall frequency of not permitted (unhealthy) food advertising (±SD; standard deviation) per hour was 2.90 ± 3.22 (2016), 2.66 ± 3.55 (2017), or 2.13 ± 3.04 (2018) ads/h/channel. The frequency of not permitted food ads decreased to 0.02 ± 0.01 per h/channel during cartoons and other children's programmes in 2018. The new Slovenian food marketing regulations have reduced the advertising of unhealthy foods during children's programmes. However, children's viewership rates are also high outside of this designated programming and, as such, children's overall exposure to unhealthy food advertising is unlikely to have been reduced considerably by the regulations. Future policy interventions should be planned to cover not only children's programmes but also broadcasting periods that include the greatest numbers of child viewers. The implementation of such policies would be more challenging given that children's peak viewing times often intersect with prime time.