The aim of this study was to determine the chemical profile of monoterpenes (including identification of stereoisomers) contained in celery seed essential oil derived from waste celery seeds (Apium graveolens L.), which did not meet commercial quality criteria as a sowing material, and to evaluate the biological activity and sensory profile of the oil. The main constituent of the oil was (R)-(+)-limonene (75.06%). The antimicrobial activity of the oil was assessed using the impedimetric method to find its minimum inhibitory concentration (MIC) against the bacteria (Bacillus subtilis (MIC 50 μL/mL), Staphylococcus aureus (MIC 2 μL/mL), Escherichia coli (MIC 20 μL/mL) and Pseudomonas aeruginosa (MIC 30 μL/mL)) as well as the fungi (Candida vini (MIC 50 μL/mL), Aspergillus niger (MIC 50 μL/mL), and Penicillium expansum (MIC 50 μL/mL)). The oil showed high radical scavenging activity for DPPH (IC50 = 89.11 g/l). Fragrance perception depended on the sex of the panellists.