Achyranthes aspera is a weed of the family Amaranthaceae and grows to about 2 m high. Tagetes minuta is weed of the family Asteraceae that grows to a height of 1–2 m. The two plants are major weeds of cultivated crops. They have been documented to possess allelopathic activities. Studies have estimated that weeds generate greater losses compared to diseases and pests. That is why this research was carried out to determine the allelopathic potential of Achyranthes aspera and Tagetes minuta crude leaf extracts on the germination of maize, millet, rice, and sorghum seeds. Leaves were collected from farm fields and shade dried followed by aqueous and ethanolic extraction. Each petri dish contained five seeds that had been surface sterilized. Thirty (30) milliliters of extracts were utilized while distilled water was used as positive control. This was set up at 25 ± 2 °C in three replications adopting a completely randomized design. After 7 days, the lengths of the emerging plumule and radicles were measured, and the germination percentages were calculated. Significant inhibition of radicle and plumule lengths of maize, millet, rice, and sorghum (p ≤ 0.05) was demonstrated by the extracts. Millet recorded the highest germination percentage (89.44%), while rice recorded the lowest at 67.78%. Generally, the extracts interfered with germination and growth of these plants. Therefore, when A. aspera and T. minuta are present in farm fields, there is a substantial probability that maize, millet, rice, and sorghum will grow poorly. This could significantly lower yields, ultimately leading to food insecurity.