Membrane transport from the Endoplasmic Reticulum (ER) to the Golgi complex requires the activity of the Rab1b GTPase. It is know that Rab1b downstream effectors as well as upstream modulators are required for maintenance of Golgi structure and biogenesis; however, direct impact of Rab1b activity on these functions has not been analyzed. In this work we study, at the ultra-structural level, the ER-Golgi interface in the context of Rab1b inhibition and activation. Our results showed that Rab1b silenced cells exhibited partial Golgi fragmentation with an important increase in the number of COPII-round shape profiles. On the other hand, expression of the Rab1b active mutant (Rab1bQ67L) induced central Golgi fragmentation and the Golgi ribbon was replaced by a huge number of COPI-like-round shape profiles located in the juxta-nuclear area. Moreover, over-expression of Rab1bwt induced enlargement of the Golgi complex without modifying its normal phenotype. Our results reveal that the Golgi complex can adapt its structure in direct response of Rab1 activity. Additionally, the fact that an increase in Rab1b levels leads to Golgi enlargement suggests that Rab1b can modulate Golgi biogenesis