This study explores the application of Particleworks, a meshless CFD solver based on the Moving Particle Simulation (MPS) method, for simulating hydraulic retarders. Two distinct models were used: one for validating physical fidelity and another for conducting performance-focused design investigations. Validation results demonstrated that Particleworks closely aligns with experimental data from the reference literature, effectively capturing torque variations with rotor speed effect. A sensitivity study also emphasized the importance of particle resolution on accuracy and computational cost. Design studies using an in-house hydraulic retarder model assessed the influence of flow rate, rotor speed, working fluid, temperature, and cup geometry on braking torque. Notably, torque increased with rotor speed and steeper cup angles, while thermal effects and fluid properties significantly impacted performance trends. Comparative analysis with Star-CCM+ showed that Particleworks offers similar predictive accuracy but with substantial gains in pre-processing, setup, and runtime efficiency. These findings establish Particleworks as a robust and practical alternative to conventional CFD for rapid, iterative retarder design and analysis.