Abstract: Fractal theory has many applications in different areas, particularly in geomorphology where is a very useful tool to describe the geometrical complexity of natural systems such as stream networks. In this report, morphometry and fractal geometrical analysis was applied to estimate the fractal degree of streams networks extracted from big Chilean watersheds inserted into different tectonics and climate environments. Two different approaches were adopted, one based on Horton ratios and the second one, measuring this dimension from a box-counting algorithm. The results show that the measured fractal dimension D falls strictly in the range 1 < D < 2, showing a clear variability from one tectonics environment to another, in contrast to the results obtained from Horton’s based laws. This fractal degree can be grouped in a slope vs. drainage density diagram, revealing that drainage patterns are controlled by tectonics and hydrological erosive sculpting processes.