Slack resources have an important influence on firm’s temporary competitive advantages，however， there are conflicting views on whether slack resources will increase temporary competitive advantages. In addition，scholars know little about how slack resources are translated into firm temporary competitive advantages and what conditions enable such translation. To fill these gaps，this paper integrates the behavioral theory of the firm and resource constraints literature to explore and test a U-shaped relationship between slack resources and temporary competitive advantages as well as its mediating mechanism and moderating conditions. Our empirical research on the 279 validated questionnaires from software firms indicates: 1) slack resources have a U-shaped relationship with temporary competitive advantages; 2) slack resources have a U-shaped relationship with entrepreneurial bricolage; 3) slack resources indirectly influence temporary competitive advantages through entrepreneurial bricolage along a U-shaped path from slack resources to entrepreneurial bricolage; 4) both environmental uncertainty and resources flexibility strengthen the U-shaped relationship between slack resources and entrepreneurial bricolage; 5) environmental uncertainty and resources flexibility jointly strengthen the mediating role of entrepreneurial bricolage in the relationship between slack resources and temporary competitive advantages. The results suggest that slack resources are important sources of firm’s transient competitive advantages within the broad context of hyper-competitive conditions，while firms should be cautious about ‘middle slack resources trap’. Moreover，entrepreneurial bricolage is an important mediator between slack resources and temporary competitive advantages，particularly when the levels of environmental uncertainty and resources flexibility are high. The research conclusions have important practical implications for firms with slack resources，especially those with excess capacity.