Summary: we showed that overexpressing microRNA167A (miR167OE) in camelina under a seed‐specific promoter changed fatty acid composition and increased seed size. Specifically, the miR167OE seeds had a lower α‐linolenic acid with a concomitantly higher linoleic acid content than the wild type. This decreased level of fatty acid desaturation corresponded to a decreased transcriptional expression of the camelina fatty acid dsesaturase3 (CsFAD3) in developing seeds. Most notably, genes for seed coat development such as suberin and lignin biosynthesis were down‐regulated. This study provides valuable insights on regulatory mechanism of fatty acid metabolism and seed size determination, and suggests possible approaches to improve these important traits in camelina.