Regardless of whether a leaf is simple or compound, the mechanism underlying its development will give rise to a full comprehension of plant morphogenesis. The role of Argonaute1 (AGO1) in the development of simple leaves has been established, but its role in the development of compound leaves remains to be characterized. In this paper, a virus-induced gene silencing (VIGS) strategy was used to dramatically down-regulate the expression of AGO1 ortholog in tomatoes, a model plant for research into compound leaves. AGO1-silenced tomato compound leaves exhibited morphological defects of leaf adaxial-abaxial and trichome development. Analysis of global gene expression profiles indicated that the silencing of AGO1 in tomato compound leaf caused significant changes in the expression of several critical genes, including Auxin Response Factor 4 (ARF4) and Non-expressor of PR5 (NPR5), which were involved in adaxial-abaxial formation and IAA15 that was found to contribute to growth of trichomes as well as Gibberellic Acid Insensitive (GAI) which participated in hormone regulation. Collectively, these results shed light on the complicated mechanism by which AGO1 regulates compound leaf development.