Teams will inevitably experience negative affects when performing innovative tasks. Negative group affect would not necessarily lead to negative team outcomes. Drawing on theories of mood-as-information and mindfulness, we propose that team mindfulness will nonlinearly moderate the relationship between negative group affective tone and team innovation through the mechanism of external knowledge acquisition. We collected data from 76 research and development teams to test our hypotheses. Results indicated that 1) NGAT is positively related to external knowledge acquisition when team mindfulness is at the medium level, 2) external knowledge acquisition is positively related to team innovation, and 3) NGAT is beneficial for team innovation via external knowledge acquisition when team mindfulness is at the medium level, rather than low or high level. Theoretical and practical implications are discussed.