The aim of this article is to advance the knowledge on the theory of skew left braces. We introduce a subclass of skew left braces, which we denote by \(\mathcal {I}_n\) , \(n \ge 1\) , such that elements of the annihilator and lower central series interact ‘nicely’ with respect to commutation. That allows us to define a concept of n-isoclinism of skew left braces in \(\mathcal {I}_n\) , by using a concept of brace commutator words, which we have introduced. We prove results on 1-isoclinism (isoclinism) of skew left braces analogous to important results in group theory. For any two symmetric n-isoclinic skew left braces A and B, we prove that, there exist skew left braces C and R such that both A and B are n-isoclinic to both C and R and (i) A and B are quotient skew left braces of C; (ii) A and B are sub-skew left braces of R. Connections between a skew left brace and the group which occurs as a natural semi-direct product of additive and multiplicative groups of the skew left brace are investigated, and it is proved that n-isoclinism is preserved from braces to groups. We also show that various nilpotency concepts on skew left braces are invariant under n-isoclinism.