Synthetic pesticides are widely applied for pest and disease control in Indonesia. However, a lack of knowledge and use of Good Agricultural Practices (GAP) for safe pesticide usage among Indonesian farmers remains a problem. This study aims to investigate the gap between farmers' knowledge of GAP for safe pesticide usage and their application of it. This research was conducted in 2020 in five Indonesian provinces. Primary data collection was by means of a survey, in which 298 respondents answered structured questionnaires. The survey also identified the sources of the information recorded and the respondents’ experience of pesticide exposure. The analysis tools used were the Wilcoxon Signed Ranked Test and Importance-Performance Analysis (IPA). There were significant differences in the results of the first analysis. These results appear to confirm the results of further analysis using IPA, which show that a high level of knowledge does not mean that farmers will apply this knowledge in practice: this is particularly relevant to wearing gloves and masks, using tools to remove blockages, never clearing blocked nozzles by blowing into them, and disposing of empty containers properly. Nevertheless, in some cases high levels of knowledge do result in high levels of application. Cases of pesticide exposure affecting human health by causing symptoms such as dizziness, nausea, and vomiting confirm that GAP for pesticide usage are not being implemented properly by some farmers. It is therefore recommended that their knowledge should be enhanced through the series of technical training programs using participatory approaches, so that farmers accumulate knowledge which will drive them to adopt GAP for safe pesticide usage.