During the extraction of antioxidants from a natural product, volatile compounds are also extracted and consequently the final extract quality is decreased. Therefore, a deodorization step is necessary. The present study introduces thermo-mechanical treatment of rosemary leaves using the instantaneous controlled pressure drop (DIC) method as both deodorization and expansion process. In addition, DIC-deodorization treatment was compared with the hydrodistillation-deodorization (HD). The extraction of essential oils was achieved on dried rosemary leaves within an optimized time of 3 min by DIC and 4 h by HD. Deodorized leaves were recovered and antioxidants were extracted using solvent extraction (ethanol:water 80:20). With standard protocol extraction, rosmarinic acid of DIC-treated rosemary leaves (12.76 mg/g) was twice as much as untreated leaves (6.74 mg/g). Scanning electron microscopy (SEM) and light microscopy showed that DIC treatment resulted in profound alterations at cytohistological levels which explain the observed effectiveness of DIC process. The specific surface area calculations showed that DIC treatment allows the material to obtain a higher specific surface area. This explains the behaviour of the product towards the extraction. Overall, the results clearly revealed that DIC is an efficient method of deodorization that improved solvent extraction of rosemary antioxidants.