The application of biosolids to agricultural land has been identified as a major pathway of microplastic pollution to the environment. Very little research, however, has been done on the microplastic content of biosolids within Canada. Fifteen biosolid samples from different treatment processes (liquid, dewatered, pelletized, and alkali stabilized) were collected from eleven sources across southern Ontario to quantify and characterize the microplastic load within them. All samples exhibited microplastic concentrations ranging from 188,200 (± 24,161) to 512,000 (± 28,571) microplastics/kg dry weight, and 4,122 (± 231) to 453,746 (± 38,194) microplastics/kg wet weight. Field amendment of these biosolids can introduce up to 3.73 x 106 to 4.12 x 108 microplastic/ha of agricultural soil. There was no significant difference in the microplastic concentrations of liquid, dewatered, and pelletized samples, but a reduction in microplastic content was observed in alkali stabilized biosolids. Fragments composed 57.6% of the microplastics identified, while 36.7% were fibres. Additionally, microplastics showed an exponential increase in abundance with decreasing size. Characterization of microplastics confirmed that polyester was the most abundant, while polyethylene, polypropylene, polyamide, polyacrylamide, and polyurethane were present across the majority of biosolid samples. The results of this study provide an estimate of the potential extent of microplastic contamination to agricultural fields through the amendment of biosolids.