Abstract: Companies strive for superior results. Focusing on return, performance, and profitability is mainstream; this reasoning is constantly present in the decisions of the strategic operational management of companies. Based on this assumption, the objective of this work is to evaluate empirically whether the degree to which a company implements a combination of Just in Time (JIT) or Lean Manufacturing practices systematically affects the company's operational, financial, and/or organisational performance. For this, a meta-analysis was carried out; the final sample consisted of 28 articles, with 41 studies and 12,708 included subjects who provided the effects that explain the proposed relationship. The data were collected in the Web of Science, EBSCO, and Science Direct databases, with an open period, considering all works available until July 2020. Among the main findings, JIT practices and the company's operational performance present a positive, significant, medium effect. Lean manufacturing practices demonstrate a positive and significant relationship in operational, financial, and organisational performance, all with an average impact on the effect size. No direct relationship was found between the JIT variables and organisational performance (financial, operational, and environmental), based on the TBL. Additional research is needed regarding the relationship of JIT and Lean Manufacturing practices with the organisational performance (financial, operational, and environmental) based on the TBL, as well as an in-depth analysis of previous research related to green Lean practices and their relationship with organisational performance, based on the TBL.
