Science education in Malaysia emphasizes three components: namely knowledge, scientific skills which include science process skills and manipulative skills; scientific attitudes; and noble values. The science process skills are important in enhancing students' cognitive development and also to facilitate students' active participation during the teaching and learning process. This study is aimed at identifying the acquisition of the skill of formulating hypothesis among primary school students. It was conducted based on the theory of neo-Piagetian Cognitive Development and was investigated using generic qualitative research method. Three data collection techniques were used comprising observation, interviews and document analysis. Two tasks were developed and given to students as a stimulus during interviews: which are "Acquisition-Skill Stimulus" (RPK) and "Compilations of Experiment related Questions" (HiSET). Six primary school students were selected as participants based on purposive sampling. Based on the data analysis, four major categories emerged, namely: (a) the concept of hypothesis, (b) identification of the effect of variable, (c) the relationship between variables, and (d) testing of hypothesis. Initial findings illustrated that the mastery level of hypothesis formulation in three participants was very low, while the mastery level in the others was noticeably low.