Unfavorable weather conditions during mustard flowering and silique ripening can contribute to the formation of seeds of poor quality and low market value. Therefore, the aim of this study was to develop an effective method for separating viable white mustard seeds from the discarded fraction during the cleaning process. The seeds were divided into fractions in a pneumatic separator with a vertical aspiration channel. The weight, length, width and thickness of each seed from a given fraction were determined. The germination index was calculated for each fraction. It was found that a vertical stream of air with the speed of 4.95 to 8.25 m s–1 allows the recovery of over 65% of the seed bulk discarded during the cleaning process. A correlation analysis revealed significant relationships between the analyzed seed parameters. The highest coefficients of correlation (above 0.75) were noted between air stream velocity vs. the width, thickness and weight of white mustard seeds.