The study aimed to evaluate the nematicidal effect of powder extracts of different coloured radish seeds against Meloidogyne incognita on tomato (Gülizar F1, susceptibile to root-knot nematode) under controlled conditions. Extractions were obtained from radish seeds of different colours (white, black, red, yellow) by using ethanol and acetone solvents. The experiment was carried out using 2, 4 and 6 g powder/plant application of the extracts in the pot. The experiment was set up in a random plot design with 5 replication for each radish seed extract and concentration. Radish seed powder was applied one week after nematode inoculation (1000 M. incognita eggs). After 50 days, the number of galls and egg masses on the roots were counted. It was determined that radish colour, extraction solvents and concentrations of extracts differed significantly for their nematicidal effects. The mean number of galls and egg masses was found to be 56 units in the negative control. Compared to the negative control, all treatments and concentrations decreased the number of galls and egg masses. The number of galls and egg masses was lower in acetone extract than in ethanole extract. The nematicidal effect was higher in yellow and red radish seeds powder application. The highest nematicidal effect was determined at 6 g powder/plant application. While the mean number of galls was 1.4 unit in the yellow seed powder application at a concentration of 6 g/plant of the extract prepared with acetone solvent, it was found to be 3.0 units in the red seed powder application at 6 g/plant of the acetone extract. The number of egg masses was 1.0 unit in the yellow seed powder application, while it was 2.8 units in the red seed powder application at 6 g/plant of the acetone extract. The acetone extract of radish seed powder can be used as an alternative to chemicals in the root-knot nematodes control.