This study summarized evidence of adoption and outcomes of using Trichoderma koningii in highland agriculture in the Philippines, and estimated economic rate of returns to T. koningii R&D. Adoption rates were estimated from sales data of T. koningii pure culture, and net incremental changes based on reviewed field experiments in the Cordillera region, Philippines and partial budget analysis based on farmer interviews. Findings showed that T. koningii are being used mostly by organic and good agricultural practice producers as biofungicide for disease management, and as soil nutrient and compost enhancer. T. koningii pure culture annual geometric growth rate of sales was at 29.7% and overall adoption rate in Benguet in 2018 was roughly estimated at 0.03%. Identified constraints to adoption are: high price; misconception that Trichoderma is for organic farmers only; slow effect of the technology; limited information; and limited market outlets and marketing strategies. The estimated change in yield due to use of T. koningii ranged from 10% to 50% based on farmer interviews, and 4%–92% based on field and pot experiments in various crops and uses from literature. The net present value (NPV) assuming a 10% real social discount rate is PhP4.3 M (USD0.08M), and the rate of returns for the Philippine government investing resources in T. koningii development and promotion was estimated at 49.1% considering a 10-year period. Assuming the lowest estimate of net benefit at PhP28670 ha-1 (547 USD ha−1) and 20 years project duration, the NPV is Php3.7 M (USD 0.07M). The study contributes policy support to sustained promotion of T. koningii and continued government funding for effective biological control and biofertilizer R&D.