Although research demonstrates the key roles practical experiences play in teachers' learning to notice, few studies have examined teacher noticing in practical contexts. This study addresses the gap by exploring prospective science teachers' (PSTs) noticing in an authentic practical setting afforded through a school-based practicum associated with a block of site-based science methods and curriculum courses. With five secondary PSTs' daily journals and critical incidents they wrote as they engaged in interactions in science classes, we investigated what PSTs focused their attention on, the ways they process information to make selective attention, and how they appraised the identified events. The study design also allowed us to examine PSTs noticing variations within the same context when they worked as pairs within the same classrooms. Based on the results of the data analysis, we identified two psychological processes PSTs went through to decide what to notice, demonstrated the idiosyncratic nature of their noticing in the same practical context, and illustrated PSTs' wide range of attention and diverse ways of reasoning.