In the study; it is aimed to analyze the level of effects of organizational culture and external factors on the organizational performances of firms in the textile sector in Istanbul, named as the megapol city of Turkey, within the framework of organizational ecology approach. In the investigation which is especially over small and medium sized textile firms in the European side of Istanbul, a categorization is made between the firms that do not continue their operations and the ones that stopped operating, and with the help of the classification, a new research model is being presented. In the extent of the model, workers of these firms are being asked a questionnaire of 69 items, including 12 questions over the organizational performances, 27 over the organizational culture and 30 on the external factors. The questionnaire has filled in by the senior & middle managers, owners and shareholders of small and medium sized textile firms operating in the European side of Istanbul. The goal of the analysis is determine the role of organizational culture and external factors effects over the performances of the firms. The existence of relation between the dependent variable of firm performance and the independent variables of organizational culture and external factors links between the sub-factors of these variables are presented as statistical data. In the light of the produced output, the results are discussed, as a contribution to the future scientific studies in the academic area and to the managers, various suggestions are proposed.