Abstract: A screen-house pot experiment was conducted to assess the response of green gram (Vigna radiata L.) to the application of Minjingu Mazao fertilizer (31% P2O5) on Olasiti soil, Manyara Region-Tanzania. This study was prompted by very low or limited use of Minjingu Mazao fertilizer by smallholder farmers in the country while yields turnout of most crops, green gram inclusive, is not promising. The soil was clay with medium pH (pH 5.5-7.0) and neutral reaction (pH 6.6-7.3). The results showed that the number of pods and seeds increased from 3-6 and 7-9, respectively, at 40 to 160 mg per 4 kg soil of fertilizer applied. Similarly, the tissue N and P increased with treatment levels. The number of pods per plant and seeds per pod showed similar increase, signifying the role of these nutrients in protein synthesis in leguminous plants like green gram. Soil properties could be the spearhead to low responses obtained at low (<80 mg per 4 kg soil) and high (>320 mg per 4 kg soil) rates of Minjingu Mazao fertilizer applied. It was concluded that to optimize green gram production in Olasiti soil, Minjingu Mazao fertilizer containing 31% P2O5 should be applied at a rate of 160-320 kg ha-1 while considering other necessary agronomic practices. However, field studies to confirm the findings of this study and verify the usefulness of this fertilizer brand to green gram in Olasiti soil under field conditions could practically be the viable option before its recommendation to the smallholder farmers.