THIS INVESTIGATION was carried out in the Experimental Farm, Ghazala Village, Fac. of Agric., Zagazig Univ., El-Sharkia Governorate, Egypt, during two successive seasons (2014 and 2015) to find out the effect of biofertilization with Cyanobacteria (Anabaena oryzae, Anabaena extract and the Anabaena + Anabaena extract) under four nitrogen levels (0, 25, 50 and 75 kg N/ fad·) on growth and yield of rice (Giza 178). The obtained results could be summarized as follows: biofertilization was effective to increase significantly grain, straw, and total yields/ fad particularly when Anabaena extract was tried through rice foliage at 10 and 25 days after transplanting. Mineral N fertilization failed to increase the rice grain yield/ fad and almost all yield attributes at harvest where the check N treatment recorded at par averages as those recorded due to the addition of 50 kg N/ fad where the further increase in N level was followed by significant decrease in this respect. However, plant height and physiological attributes at heading were significantly increased due to the increase of N level to 50 kg N/ fad. The bio. X mineral fertilization interaction affected grain yield/ fad and almost all yield attributes where the response equations predicted maximum grain yield/ fad of 4.26 ton due to a predicted addition of 54.1kg N/ fad. According to these results, a complementary effect could be traced between the foliar application of Anabaena and the 50 kg N/ fad level to maximize the grain, straw, and total yields/ fad. An eutrophication effect could had been taking place when Anabaena was soil added due to over growth by the algae particularly, during rice grain filling where a possible toxic effect and nutrient imbalance could have had played a role in ceiling the favourable effect of biofertilization observed up to heading particularly on plant height and greeness of leaves which was expressed in their content from chlorophyll and carotenoids.