Previous research has shown that the dairy industry in Serbia is more profitable than the market average measured by indices of the Belgrade Stock Exchange BELEX15 and BELEXLINE. The labour costs are, after raw milk costs, the second most important group of costs in dairy processing industry. The aim of this paper is to identify changes and adaptations of modern industry market conditions through analysis of labour cost of dairy processing industry in Serbia, by analysis of the trends in the number of employees, average labour cost, and productivity and cost efficiency and through the prism of these changes. In this paper, on qualified sample is proved that there is a strong positive correlation between firm size and productivity and a weaker one between firm size and labour costs. On the other hand, contrary to previous research, relation between the size of companies in the sample and the economic efficiency of labour costs was not confirmed.