On top of being a prominent source of calories for more than half of the world’s population, cultivated rice (Oryza sativa) provides beneficial effects for human health through several bioactive compounds, including phenolics. To earn this advantage, it is essential to assess the profile of these compounds through appropriate cooking practices. In this study, the compositions of 18 individual phenolics contained by different cultivars (pigmented and non-pigmented rice) were evaluated during cooking processes. The level of the studied compounds dramatically decreased throughout a series of cooking processes in addition to the changes on the composition of phenolic acids and their aldehydes in the grain. Substantial losses was occurred particularly due to heating processes starting at 10 minute adjacent to the alteration of the compositions of phenolic compounds. Regardless of rice varieties, the concentration of phenolics decreased severely and remained merely 35 to 55% compared to the initial level in raw grains. This finding confirms that the stability of some phenolic compounds is adversely affected by heat. Additionally, no clear differences were found for the sensitivity of individual phenolics to degradation during the cooking steps, but most of them showed similar trend of degradation.