Following fundamental changes in the competitive landscape, some research focuses on how product market competition affects corporate investment. In fact, labor costs account for more than two-thirds of the value added of the economy as a whole and represent a significant portion of total production costs. Accordingly, the present study examines the relationship between competition in the product market and the efficiency of manpower investment. The present research is applied in terms of purpose and is methodological in terms of causal (post-event) research. The statistical population of the research is the companies listed on the Tehran Stock Exchange and using the method of systematic elimination of 141 companies as a research sample in the period between 2014 to 2020 was selected. The results showed that competition in the product market and the efficiency of manpower investment improves. Thus, although recent studies show a prominent role of product market competition in shaping firm R&D and investment decisions, the results of such studies can not be used to infer the impact on labor investment decisions. This is because capital and labor investments are different in terms of adjustment costs, which indicates an important driver of investment strategies and differences in the impact of competition on the company's labor and investment.