Flow stability plays a key role in transition to turbulence in various systems. This transition initiates with disturbances appearing in the laminar base flow, potentially amplifying over time based on flow and fluid parameters. In response to these amplified disturbances, the flow undergoes successive stages of different laminar flows, ultimately transitioning to turbulence. One influential parameter affecting flow stability is the nanoparticle volume fraction (Ï) in nanofluids, extensively employed in thermofluid systems like cooling devices to enhance fluid thermal conductivity and the heat transfer coefficient. Focusing on the impact of nanoparticles on JefferyâHamel flow stability, this study assumes fluid properties are temperature- and pressure-independent, exclusively examining the momentum transfer aspect. The analysis commences by deriving the base laminar flow solution. Subsequently, linear temporal stability analysis is employed, imposing infinitesimally-small perturbations on the base flow as a modified form of normal modes. A generalized OrrâSommerfeld equation is derived and solved using a spectral method. Results indicate that, assuming nanofluid viscosity as ÎŒnf=ÎŒf/(1âÏ)2.5, nanoparticle effects on momentum transfer and flow stability hinge on the ratio of nano-solid particle density to base fluid density (RÏ=Ïs/Ïf). For Ïâ(0,0.1], flow stabilization occurs with Ï when RÏ<3.5000, while destabilization is observed when RÏ>4.0135. Notably, nanoparticles exhibit a negligible impact on flow stability when 3.5000â€RÏâ€4.0135.