In recent times gentrification in the form of urbanisation has become a prominent recurrent phenomenon dotting the cityscape on most developing cities in the global south. Little attention has been given to the process because the dynamics of gentrification has become more challenging to city managers in Port Harcourt Municipality in Nigeria. This study aims to highlight specific areas inundated with gentrification within selected neighbourhoods of Port Harcourt Municipality such as Orije Old GRA, Oromenike (D/Line) and PH-Township with characteristics of three residential densities (low, medium and high) respectively. Identify causal factors with a view to understanding the dynamics and recommend planning measures that would ameliorate associated identified impacts. Mixed method approach was deployed. A total of 397 respondents across three selected neighbourhoods participated with the aid of closed and open-ended questionnaires to obtain the data. Findings indicate significant changes in the neighbourhoods different from their original designated uses: from residential to mixed uses (commercial and residential) with impact on the social and economic conditions of these neighbourhoods. Sustained demand for space for other uses in addition to increasing population result in sudden spike in rent for residential and other uses. The study recommends intensive periodic review of existing planning schemes establishing these neighbourhoods by both government and relevant physical planning agencies as this would upgrade the neighbourhoods to more sustainable and modern urban environment; construction of more low-cost housing units in these neighbourhoods especially in the high and medium densities neighbourhoods for residents to ameliorate the high rental values of existing properties; introduction of rent control mechanisms to checkmate arbitrary increase in rent in the neighbourhoods, discourage unapproved change of use; and strict penalties according to the Rivers State Physical Planning and Development Law of 2004 to developers that violate the alteration of buildings without permit and going against the conditions of the permit issued to the developers to alter any building.