Agile practices are activities or procedures that are applied during the software development process in order to improve its quality and productivity. The objective of this study is to determine the influence of agile practices on software quality. For this purpose, a model composed of 4 groups of agile practices and 8 quality characteristics according to the ISO/IEC 25010 standard has here been proposed. The results of 146 questionnaires addressed to people involved in the software development process show that the application of agile engineering and project management practices have a significant positive influence on the quality attribute functionality. On the other hand, project management practices have a low impact on the quality characteristics of compatibility, portability, security, and usability.