Biodiesel production in conventional batch reactors is limited by long residence times and mass transfer constraints due to the immiscibility of oils and alcohols. Microreactor technology offers process intensification through high surface-area-to-volume ratios and enhanced mixing. This review synthesizes seventeen key studies on biodiesel synthesis in microchannel reactors. Passive micromixers with optimized geometries significantly enhance performance. T-channels with alternate circular obstructions achieved mixing indices of 0.99 and conversions of 99.09%. Uniflow comb micromixers achieved high mixing quality with pressure drops ten times lower than cross-shaped designs. Tesla-shaped microreactors produced 96.7% yields, outperforming omega (95.3%) and T-shaped (93.5%) configurations. Key challenges include developing biphasic kinetic models, managing the mixing-pressure drop trade-off (up to 178 bars), fabricating reliable seals for polymer reactors, accommodating lower-quality feedstocks, implementing online monitoring, and ensuring uniform flow distribution in scaled-up systems. Addressing these gaps will enable distributed, small-scale biodiesel production