2020-12-222020-12-212020-12-222020-12-10https://ri.ucsal.br/handle/prefix/2688This article analyzes the legal interest that determines the appropriateness of the intervention of third parties in typical and atypical legal affairs and seeks to understand the requirements that the magistrate takes into account when assessing the presence of this procedural assumption when admitting the third party in the process. Legal interest and legitimacy are fundamental requirements to be exposed in the initial petition. Consequently, several theories emerged explaining how the verification of these conditions required by law should be, among these doctrinal currents, the assertion theory stood out. For this, this work adopted an exploratory methodology, through bibliographic research, jurisprudential, supported by the legislation on the subject.Acesso AbertoInteresse jurídicoTeoria da asserçãoIntervenção de terceiroLegal interestAssertion theoryThird party interventionTrabalho de Conclusão de CursoCiências Sociais AplicadasDireito