Despite a high productive potential for many best bet agricultural technologies, there is a low rate of adoption from farmers. Recommendations of improved technologies such as fertilizer use based on agronomic data without economic analysis contributes to this low adoption rate. The purpose of this study was to evaluate the profitability of selected fertilizer types and rates in maize production in a sub-humid farming system. A field experiment was conducted to investigate costs and revenue of fertilizer types and rates applied on maize farms using a split-plot layout under randomized complete block design. The phosphate fertilizers trialed were local Minjingu Mazao (MM), diammonium phosphate (DAP) and triple super phosphate (TSP), urea was used to supply nitrogen. Fertilizer rates were micro-doses at 12.5%, 25%, 50% and 75% compared to control and recommended rates. Local MM at 75% micro-dosing produced the highest net benefit 3.0 – 3.5 million Tanzanian Shillings per hectare (TZS/ha) followed by 2.7 – 2.9 million TZS/ha from TSP at recommended rates and DAP at a 75% micro-dose rate under subsistence farming. Micro-dosing fertilizer at 25% and 50% produced the highest benefit-cost ratio under both commercial and subsistence farming conditions. Micro-dosing at a rate of 12.5% was more profitable than the control rate and farm profitability increased towards 25% and 50%, thereafter decreasing as application approached the recommended rate. Adoption of micro-dosing fertilizer at 12.5% could be an entry point to fertilizer use and to later be advanced to 25% and 50% micro-dosing rates which are more profitable under smallholder farming systems in sub-humid tropics.