The crime with the highest criminal weight in Peru is the omission to provide child support. The objective was to identify the effectiveness of the application of the principle of the best interest of the child in the process of omission of child support. In a population of 90 mothers, the sample was non-probabilistic by convenience, exploratory level, basic type and non-experimental design; the technique used was the survey; in the results it was obtained that 20.00% consider the process of the crime of omission of child support deficient and 11.11% indicate that this process is adequate; likewise, 18.89% consider that the application of the "Best Interest of the Child" is not considered and 8.89% consider that its application is correct. In conclusion, the application of the principle of the Best Interest of the Child is deficient in the process of failure to provide child support.