Most studies on fidelity focus on adherence (how much it is done), ignoring quality of delivery (how well it is done) as a measure of implementation, and are mainly quantitative in nature. In-depth qualitative studies assessing how much and how well curricula are implemented are scarce. Drawing on data from a qualitative study, this article addresses both the adherence and the quality of delivery dimensions of a newly developed life sciences curriculum. The study also seeks to identify the factors affecting fidelity of implementation. Evaluative case study design, in which the required data were gathered through semi-structured interviews and classroom observations, was used. Sixteen primary school teachers participated in the study, and the data were analysed through thematic analysis. Findings reveal that the participating teachers focus solely on knowledge transmission while also making adaptations to the curriculum. The study highlights the striking role textbooks play in the implementation process. The findings provide strong evidence for urgent needs in organising professional development for teachers to equip them with competencies to implement the curriculum with fidelity.