Chicorium spinosum L. (or spiny chicory) is a wild edible species that can be found in different coastal areas of the Mediterranean basin. During the last few years, its chemical composition has been described in detail and its bioactive compounds content is correlated with the prevention of various chronic diseases and disorders. In this experiment, various fertilization regimes were tested aiming to reveal the nutrient requirements of the species and how fertilization may affect the chemical composition and the bioactive properties of edible leaves. Seven fertilization treatments varying in the amounts of N:P:K (namely, 100:100:100; 200:100:100; 200:200:200; 300:100:100; 300:200:200; 300:300:300 ppm of N:P:K, and control where no fertilizers were added) were applied via nutrient solution feeding in pot-grown C. spinosum plants. The growth parameters tested included the number and the fresh and dry weight of leaves, SPAD index, leaf area index (LAI) and specific leaf area (SLA). Bioactive parameters, including the antioxidant (OxHLIA and TBARS assays), anti-inflammatory (RAW 264.7 cell line) and cytotoxic (PLP2, AGS, CaCo2, VERO and MCF7 cell lines), and phenolic compounds content were examined in aqueous and hydroethanolic extracts of leaves. Regarding the growth parameters, the highest number of leaves was recorded for the 300:200:100 treatment, while the highest fresh weight was noted for the 200:100:100 treatment. The control treatment had the highest dry weight of leaves, while the highest LAI and SLA values were observed for the 200:100:100 and 300:10:100 treatments, respectively. Finally, the highest SPAD values were detected for the 200:200:200 treatment, without being significantly different from the control. In the case of hydroethanolic extracts, the highest antioxidant activity for the OxHLIA and TBARS assays were recorded for the 100:100:100 and 300:100:100 treatments, respectively, whereas the treatments of 200:100:100 and 100:100:100 showed the best results for OxHLIA and TBARS assays in the aqueous extracts. Both extracts, did not show cytotoxic or anti-inflammatory activities. Nine phenolic compounds were detected in both extracts, including two phenolic acids and seven flavonoids, with the major compounds being 4-O-p-coumaroylquinic acid and isorhamnetin-O- hexuronoside, regardless of the extraction method. In the case of hydroethanolic extracts, the treatment of 300:300:300 contained the highest amounts of total phenolic acids, while the plants treated with 300:100:100 had the highest content in total flavonoids and total phenolic compounds. Finally, the highest content of total phenolic acids, total flavonoids and total phenolic compounds for the aqueous extracts was recorded in the treatment of 300:300:300. In conclusion, the application of fertilizers on C. spinosum plants had positive effects on plant growth, especially the 200:100:100 treatment where the highest fresh yield was recorded, while variable effects of fertilizer regimes on the chemical composition and bioactive properties were recorded.