Sulphur is the fourth most important plant nutrient after nitrogen, phosphorus, and potassium, and it is becoming increasingly crucial in high-quality crop production (Bhoyar., 2019). Since limited work has been carried out regarding different sulphur sources on cabbage production in the Coimbatore district, the present study was undertaken to investigate the sulphur sources and levels on various biochemical constituents of cabbage. Hence a field experiment was conducted in the farmer’s field at Viraliyur village, Thondamuthur block of Coimbatore district, Tamil Nadu to assess the effect of sulphur fertilization on improving the biochemical constituents of cabbage hybrid Saint. There were four different S sources (Elemental sulphur, Potassium sulphate, Gypsum, Single super phosphate) applied at five levels (0, 20, 40, 60 and 80 kg ha-1) and replicated thrice in a factorial randomized block design. The crop was fertilized with a Soil Test Crop Response-prescribed dose of NPK (200:125:25 kg ha-1). The crop was harvested on 90th day and cabbage heads were analysed for various biochemical constituents like ascorbic acid, total soluble solids (TSS), titratable acidity (TA), chlorophyll content, glucosinolates (GLs), total phenol content (TPC), sulphur containing amino acid (methionine) and antioxidant enzyme activity (peroxidase). The influence of S fertilizers on biochemical constituents increased significantly with increasing levels of sulphur fertilization up to 80 kg S ha-1 excluding ascorbic acid content. The pooled data showed that gypsum applied at 80 kg ha-1 registered the maximum GLs (69.0 µmol g-1), TPC (31.9 mM 100g-1), methionine (32.3%), peroxidase activity (0.70 units min-1mg-1), TSS (7.64 0Brix), TA (0.64%), ascorbic acid (61.4 mg 100g-1) and total chlorophyll (1.21 mg g-1) in cabbage head. The lowest content of biochemical constituents viz., GLs (34.1 µmol g-1), TPC (8.10 mM 100g-1), methionine (17.6%) and peroxidase (0.31 units min-1mg-1) were observed in control applied NPK alone. There were positive and significant changes in the biochemical constituents of cabbage due to S application which confirms the improvement in the quality of cabbage head. The study concluded that gypsum was the better sulphur source for improving the quality of cabbage.