PurposeThe purpose of the paper is to explain the impact of workplace flexibility on managers' perceptions of firm performance. The research focuses primarily on outsourcing, an increasingly common way of creating workplace flexibility, by studying its antecedents based on several economic and organisational theories.Design/methodology/approachThe methodology is a postal survey to a sample of 156 Spanish firms and statistical analysis.FindingsThe findings suggest that it is important to take into account different theoretical perspectives to explain the intensity of outsourcing: all proposed antecedents of the intensity of outsourcing except differentiation strategy and cooperation are significantly associated to outsourcing. There is not any significant relationship between outsourcing and firm performance; workplace internal flexibility does impact on firm performance but external flexibility does not. However, the results change according to the category of core and peripheral outsourcing.Research limitations/implicationsThis study's single country setting could limit the generalizability of the findings. Longitudinal as opposed to cross‐sectional data are needed for studying the causal assumptions reported here. Future studies should also take a multiple‐source as opposed to a single‐source data collection approach. Finally, objective measures of outsourcing and firm performance, as well as moderated variables are needed to analyse differentiated impacts on firm performance.Practical implicationsThis research makes two contributions to both practice and theory. First, the results show that the perceived impact of outsourcing on sub‐factors of firm performance is positive for peripheral activities and negative for core activities. Second, the research provides a framework to analyse the antecedents of outsourcing and the concurrent impact of outsourcing and other workplace flexibility dimensions on firm performance.Originality/valueThe paper explains outsourcing decisions by antecedents based on several economic and organisational theories. It also analyses the concurrent impact of outsourcing and other workplace flexibility dimensions on firm performance.