Different methods of cooking affected nutritional levels of vegetables, which were found to be based on habit and society. Ten commonly consumed green leafy vegetables; thorny tree, dill, chinese chive, peninsular, asiatic pennywort, betel vine, garden parsley, vietnamese coriander, swamp morning glory and sweet basil were investigated for the effects of Thai domestic blanching and streaming on chlorophylls, carotenoids, total polyphenol content (TPC) and total antioxidant capacity (TAC). Blanching for 30 s significantly (P < 0.05) enhanced contents of chlorophylls, lutein, β-carotene, TPC and TAC in most tested vegetables. A significant correlation (P < 0.05) among chlorophylls and β-carotene (r = 0.888), lutein and β-carotene (r = 0.784), pheophytin and TAC (r = 0.615, DPPH and r = 0.568, FRAP), TPC and TAC (r = 0.965, DPPH and r = 0.959, FRAP) were also found. After 5 min streaming, TPC and TAC showed similar patterns which were higher and lower in some cooked vegetables compared to fresh samples. Chlorophylls significantly changed to pheophytins during streaming. Alteration of pheophytins enhanced TAC as a significant correlation was obtained (r = 0.727, DPPH) and r = 0.713, FRAP) in streamed vegetables. Results demonstrated that 30 s blanching better preserved and also promoted more nutrients and antioxidant properties in green leafy vegetables than streaming.