A field experiment was conducted during 2011 and 2012 seasons to evaluate the effect of cyanobacterial foliar application with different levels of chemical fertilizers (25%, 50% and 100% of the recommended dose of NPK fertilizer) on the growth characters, macro-elements content, essential oil percentage, yield and composition, total phenol content, total flavonoid content as well as the antioxidant activity of marjoram (Origanum majorana L.) plant. The cyanobacteria (Blue green algae) belonging to the strain Spirulina platensis were used as a foliar spray at four concentrations (0, 4.5, 7.5 and 10 g/l). The obtained results revealed that the application of cyanobacteria combined with 50 or 100% of the recommended dose of NPK fertilizer improved growth characters, chemical constituents and essential oil composition than the other treatments. So, using cyanobacterial foliar spray with 50% of the recommended dose of NPK fertilizer could provide a high quality product with reduced harmful agrochemicals and eliminate environmental pollution.