Abstract <p>As an important fragrant fresh cut flower, the flowering period and blooming characteristics of <i>Freesia hybrida</i> Klatt. have a crucial impact on the quality of fresh cut flowers. Therefore, it is of great application value and economic benefit to study how to prolong its flowering period and improve the quality of flowers. In this study, ‘Red Lion’ (<i>F. hybrida</i> Klatt.) was used as the experimental material to investigate the effects of different concentrations of exogenous brassinolide (BR) on the extension of the flowering period and physiological properties of <i>F. hybrida</i>, in order to provide technical support for flowering regulation and cut flower cultivation of <i>F. hybrida</i>. The results showed that exogenous BR treatment could significantly prolong the flowering period of ‘Red Lion’ and improve the quality of flowers. Compared with the control, spraying 0.5 mg/L BR was beneficial to prolong the flowering period of ‘Red Lion’, which was extended by 11 days; it also significantly increased the flower diameter, scape length, and plant height by 63.25, 11.5, and 7.04%, but the number of florets per scape decreased. Additionally, under this treatment condition the soluble sugar content and the activities of antioxidant enzymes such as peroxidase, catalase, and superoxide dismutase in leaves were enhanced, which were 5.6, 146.92, 33.58, and 150.26% higher than those of the control. Furthermore, compared to the control, the photosynthetic efficiency of <i>F. hybrida</i> was enhanced under the concentration of 0.1 mg/L BR, <i>F</i>_o/<i>F</i>_m decreased by 4.91%, <i>F</i>_v/<i>F</i>_m and PI abs increased by 1.1 and 7.42%. At the same time, the length of scape increased by 17.04% and the soluble protein content increased by 8.31%. Our results showed that exogenous BR could prolong the flowering period, increase the flower diameter and scape length of ‘Red Lion’.</p>