Mitochondria are organelles involved in energy metabolism and biosynthesis. As the metabolites released from mitochondria are raw materials used for lipid synthesis, mitochondria also play important roles in lipid metabolism. Here we report that Slc1, a 1-acylglycerol-3-phosphate O-acyltransferase in the fission yeast Schizosaccharomyces pombe, is required to maintain tubular mitochondrial morphology and normal mitochondrial functions. The absence of Slc1 causes mitochondrial fragmentation, increases mitochondrial fission frequency, reduces mitochondrial respiration, and slows down nitrogen starvation-induced mitophagy. In addition, the absence of Slc1 significantly increases the protein level of Ptl2, which is the triacylglycerol lipase localized on lipid droplets. The phenotypes caused by the absence of Slc1 depend on its acyltransferase enzymatic activity. Therefore, our study uncovers new roles of a lipid synthesis enzyme Slc1 in regulating mitochondria and lipid droplets.