Organic amendments can be used as a sustainable supplement or alternative to synthetic fertilizers. However, yield response to organic amendments is difficult to predict because applied nutrients must be mineralized in the soil after application – a process driven by a complex suite of soil properties. The objectives of this meta-analysis were to 1) estimate a global mean yield response to organic amendments, and 2) to determine factors driving variability in that yield response. We compared data from 53 unique studies to determine the first-season yield response to organic amendments (without supplemental synthetic fertilizer) compared to a non-fertilized control. Information about amendments (type, rate, and nutrient analysis), crops, cultural practices, soil properties (texture, fertility, and organic matter content) and local climate were extracted from each study and used to assess possible drivers of yield response. Across all studies, crop yield increased by 43% in the first-season after organic amendment of any type or rate. Yield response was greatest for leafy crops (>70% increase) and lowest for root/tuber/bulb crops (<30% increase). Poultry manure/compost was the most commonly used amendment and provided a yield increase of nearly 80%. In contrast, plant-based amendments (e.g., yard-waste compost) increased yield by less than 30%. Surprisingly, amendment application rate (on a dry weight or nitrogen basis) was not an effective predictor of yield response. Yield response was muted in soils with high organic matter content and in arid climates. Results may help to inform future strategies for maximizing the agronomic value of recycled organic waste.