<p>The widespread presence of microplastics (MPs) as emerging contaminants in soil has become a major concern, with organic fertilizers extensively used in agriculture being potential sources of soil MPs. In this study, eight commercially available organic fertilizer products were randomly purchased from the market and characterized for their static properties, as well as their status after being applied to soil as inputs. The study revealed that 100% of the tested commercial organic fertilizers contained detectable MPs, with average and maximum abundances of 2,547 ± 427 and 9,454 ± 2,151 items·g^− 1, respectively. The aspect ratio of most MPs in commercial organic fertilizers was less than 10, with small-sized MPs (aspect ratio of 1–5) accounting for 71% of them. The accumulation of MPs in commercial organic fertilizers was positively correlated with pH, available potassium, and heavy metal content, with contributions ranging from 4.6 to 13.3%. After the application of commercial organic fertilizers into the soil, the abundance of MPs in the soil significantly increased along with the soil temperature and moisture, while being adverse to the particle size. The potential long-term accumulation of soil MPs resulting from prolonged and exclusive use of organic fertilizers raises concerns as a new agricultural issue that warrants sustained attention.</p>