<p><i>Meloidogyne javanica</i> threatens agricultural profitability due to the lack of effective control strategies. This study investigated the nematicidal potential of phosphate sludge-enriched composts for the control of <i>M. javanica</i> on tomato plants under organic cultivation at nursery level. Three composts, PS-SBW (20% phosphate sludge, 70% food waste, 10% sugar beet waste), PS-GW (20% phosphate sludge, 70% food waste, 10% green waste), and PS-OMW (20% phosphate sludge, 70% food waste, 10% olive mill waste), were tested at 1%, 2%, 5%, and 10% concentrations to assess morphological and physiological variations against an inoculated and non-treated control. The composts exhibited normal pH (7.065–7.85) and electrical conductivity (EC), except for PS-GW (4.87 mS cm⁻¹). PS-GW at a concentration of 10% significantly increased plant growth parameters, specifically, plant height (37.95%), shoot fresh weight (282.93%), shoot dry weight (179.45%), root weight (178.05%), and root diameter (88.29%) when compared to the inoculated and non-treated control. In contrast, PS-OMW at 5% proved to be the most effective in reducing the <i>M. javanica</i> final population (83%), reproduction factor (83%), and gall index (40%) when compared to the inoculated and non-treated control, as well as chlorophyll a, and carotenoids were significantly increased, while chlorophyll b increased with PS-GW at 10%. PS-SBW at 2% and PS-GW at 10% decreased the total phenolic compound (TPC) and flavonoid content (TFC), while PS-OMW showed an increase in secondary metabolites. Phosphate sludge-enriched composts, especially PS-GW and PS-OMW, effectively improved organic tomato growth and suppressed <i>M. javanica</i> growth, while PS-SBW showed intermediate effects of <i>M. javanica</i> control and tomato growth enhancement. Their distinct effects on plant growth and nematode control suggest there is a need for additional research to explore possible complementary effects when used in combination.</p>