Micro-enterprises have an important place in the French economy with a share of 9% in the GDP. The management of their capital structure is a central element to guarantee their activity and development. This article proposes to study the determining factors of the capital structure of a sample of more than 4000 French micro-enterprises over the period from 2003 to 2013, with a focus on the impact of the 2007-2008 crisis. Our results show that micro-enterprises favor internal financing over external financing. During the crisis, micro-enterprises rely more on short-term debt to secure operational growth while limiting long-term debt to finance investments in tangible assets.