An experiment was done to see the allelopathic effect of Parthenium hysterophorus on the seed germination and seedling growth of maize (Zea mays) in laboratory conditions. The results showed that seed germination was negatively affected by the aqueous stem extract of Parthenium in different concentrations (15, 25, 50, 75 and 100%) when compared to control condition. Seed germination in control was 100% whereas this value was 3.33% in 100% of stem extract. Stem extract of P. hysterophorus on shoot length was more affected than the root length. T-test values for root length between control and 50, 75 and 100% were positively and significantly different at p<0.001; and for shoot length these values for different treatments were significantly different at p<0.001.