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Basement membranes (BMs) play important roles under various physiological conditions in animals, including ecdysozoans. During development, BMs undergo alterations through diverse intrinsic and extrinsic regulatory mechanisms; however, the full complement of pathways controlling these changes remain unclear. Here, we found that fat body-overexpression of <i>Drosophila miR-263b</i>, which is highly expressed during the larval-to-pupal transition, resulted in a decrease in the overall size of the larval fat body, and ultimately, in a severe growth defect accompanied by a reduction in cell proliferation and cell size. Interestingly, we further observed that a large proportion of the larval fat body cells were prematurely disassociated from each other. Moreover, we present evidence that miR-263b-5p suppresses the main component of BMs, <i>Laminin A</i> (<i>LanA</i>). Through experiments using RNA interference (RNAi) of <i>LanA</i>, we found that its depletion phenocopied the effects in <i>miR-263b</i>-overexpressing flies. Overall, our findings suggest a potential role for miR-263b in developmental growth and cell association by suppressing <i>LanA</i> expression in the <i>Drosophila</i> fat body.