This study investigated grade 4 learners' understandings about the Nature of Scientific Inquiry (NOSI) in primary schools within the South African context. A qualitative methodology was employed using a framework of five knowledge aspects about the NOSI in assessing learners' understandings about the ways scientists investigate the natural world. Four different school types and 152 grade 4 learners from South African primary schools participated in the study. Data were collected using the open-ended Views About Scientific Inquiry-Elementary (VASI-E) questionnaire. Findings from data analysis indicated that, over 70% of grade 4 learners held naïve understandings about all five aspects of the NOSI investigated in the study. The findings also revealed some observed differences in NOSI understandings across the different school types. Based on these findings, the researchers concluded that, there is a need for primary school learners to acquire baseline knowledge about the NOSI by engaging in learning tasks that scaffold their understandings on how scientific knowledge is generated. Also, that the NOSI should be explicitly addressed by involving learners in inquiry activities on questioning, data collection, observation, and interpretation. These findings have direct implications for primary school teachers and teacher educators for enacting science as inquiry.