Small- to medium-sized enterprises (SMEs) are recognized as drivers of economic growth, yet commonly face low innovation and organizational success due to insufficient cross-functional integration. We pose the simple question: what factors hinder cross-functional integration from occurring? We analyse cross-functional integration at management level by developing the framework of dominant ideological modes of rationality, composing professional identity, power relations and rationalities and through the construct of ‘members’ categorization devices’ (MCDs). The article builds theory from a longitudinal in-depth empirical investigation of ‘everyday’ micro-political processes involved in cross-functional integration by drawing on political and ethnomethodological perspectives. It provides novel findings on the dynamics between power relations and cross-functional integration, the influence of ‘thought worlds’ of different functions involved in the innovation process, and contributes empirical evidence that professional identity produces power relations and rationality. Implications for theory, method and practice are considered.