<p>Modern microchannel heat sinks (MCHS) with improved heat transfer capabilities provide appealing options for effectively cooling high-heat-flux electronics. Recent studies with the novel inverted T-shaped with semicircular ends at base (ITSCEB) MCHS have shown its preeminence in high heat flux scenarios. In this study, both experimental and computational investigations were conducted to report the thermohydraulic behavior of an ITSCEB microchannel with a hybrid CNT-oxide nanofluid. The experiments were performed with different concentrations of the hybrid (Al₂O₃ + CNT (1:1)/water) nanofluid (HyNF) with varying volume fractions of Al₂O₃ + CNT (0, 0.001, 0.005, 0.01 vol%) for a given heat flux. The numerical results using a two-phase mixture model were validated with the experimental results and existing literature. It was observed that with an increase in volume fraction, heat transfer performance and pressure drop also increased. The enhancement is attributed to particle deposition aiding nanoconvection in the flow. The average heat transfer enhancement recorded for 0.01 vol% HyNF was approximately 5.47%. Numerical investigations were also carried out with various mixture ratios (CNT:Al₂O₃) of 0.01 vol% hybrid nanofluid. No significant deviation in performance was reported with different mixture ratios of the hybrid nanofluid in the ITSCEB microchannel. Finally, the authors proposed a universal correlation for heat transfer for various cross-sections of microchannels using data from the present and previously reported studies using water-based nanofluids.</p>