The usage of microchannels in heat dissipation of compact electronic and high computing devices has been explored extensively in the last three decades. Microchannels of different shapes are widely investigated in the literature but limited data is available for parametric studies of fluid flow and heat transfer in triangular microchannels. In the current work, a three-dimensional modeling is done for heat transfer and fluid flow in triangular miniature channels of different geometry. The effect of channel apex angle and channel depth in the heat transfer and fluid flow characteristics is numerically investigated. Conjugate heat transfer is analyzed for constant heat flux and fixed mass flow rate. The thermohydraulic behavior of the channels of 1 mm depth having different apex angles is simulated. The result shows better heat transfer characteristics with decrease in channel apex angle but the pressure drop through the channel increases on reducing the channel angle. For the same apex angle, the heat transfer coefficient and pressure drop of fluid flow decreases with increase in channel depth. The average fluid velocity is larger for the low apex angle channel of same depth. Investigation is also performed for different Reynolds numbers to analyze its effect on heat transfer and fluid flow.