The objective of this master thesis is to analyze the nuances involving the liability of the third party that instigates the break of negotiations regarding a contract in which he would not be a party. In Brazilian legal system, the theories of pre-contractual liability and complicit third party are already consolidated, however, the material that analyzes the junction of the two institutes is still scarce. The application of these two institutes is seen with caution, avoiding exacerbated interference in acts of autonomy and free competition. However, this cannot exempt the third party from being liable for the illicit act he practiced, representing a safe-conduct for him to improperly interfere in other relationship. The first part of this master thesis addresses the concept and aspects involved in the pre-contractual civil liability for break of negotiations and in the study of the complicit third party. In turn, the last chapter is dedicated to the comparison between the two institutes, analyzing the similarities between them and in which way the differences may be overcome to allow the liability of the third party that interferes in the pre-contractual phase. From this comparison, there are grounds to support the application of the theory of the complicit third party in the pre-contractual phase, if the requirements analyzed in this study are met.