Root-knot nematodes (Meloidogyne javanica) are among the most destructive pests of sweet pepper (Capsicum annuum). Sustainable alternatives to chemical nematicides are urgently needed. This study evaluated the synergistic effects of Paecilomyces sp. and the seaweed Padina boergesenii (powder and extract) on nematode management and plant growth. In vitro assays tested three concentrations of Paecilomyces sp. (10⁴, 10⁶, and 10¹⁰ conidia mL⁻¹) and different concentrations of P. boergesenii on juvenile survival and egg hatching. Greenhouse experiments employed the most effective fungal concentration (10¹⁰ conidia mL⁻¹) in combination with P. boergesenii powder or extract to assess nematode infestation, plant growth, pigment contents, and antioxidant activities. Paecilomyces sp. showed strong nematicidal activity, while P. boergesenii alone was moderately effective. When combined, particularly with the powder form, the treatments significantly reduced galling and nematode reproduction while enhancing plant growth, chlorophyll content, and antioxidant enzyme activities. The integration of Paecilomyces sp. with P. boergesenii offers a promising eco-friendly strategy for controlling M. javanica and promoting sweet pepper resilience, supporting its use in sustainable integrated pest management.