Bangladesh is a South Asian post-colonial state with fourth largest Muslim population in the world.  The size of Bangladeshi diaspora in many of the big cities in the West is increasing steadily since last couple of decades. The main thrust of this paper is to shed light on the pattern of socio-cultural interaction of Bangladeshi diaspora with the mainstream in two big cities in Europe – Madrid and London.  The way the Bangladeshis involve or maintain a distance with the mainstream politics will also be analyzed here. This paper endeavors to explain the factors determine the interaction pattern of the Bangladeshi diaspora and explain the reasons if there is a trend of collective disengagement or an indication of integration. Examining these realities is important in this era of religious extremism and populist nationalism in the West.  In this venture, this paper tries to develop a ranking system of the determining factors - language, cultural difference, economic condition, fear factor, inward looking lifestyle, religious restrictions and so on. A scientifically arranged survey along with appropriate secondary documents constitutes the findings and recommendation part of this article.