Street vendors are defined as informal traders who sell their goods or services whether or not it has fixed location for conducting business. They are generally found in most of the cities of poor developing countries. In the Kathmandu valley cities of Nepal, the petty street traders consist of features such as temporary structure, small size, self-employment, low investment, low skills and marginal groups. They are also known as ‘invisible economy’ and contribute largely to the national economy indirectly. The data for this paper were acquired from standard observation protocol sheet, GPS, informal discussions with the vendors based on checklist and available existing documents. This paper explores that ‘convenient’ is one of the most crucial factors to determine the variation in the spatial location pattern of the petty street vendors in the Kathmandu valley cities. GIS and the nearest neighborhood technique were used to identify the spatial pattern of the petty street vendors. The paper also briefly describes the historical account of the evolution of informal marketing activities in the Kathmandu valley cities. It is found that the petty vendors are mostly migrants with petty trading as their only income source, and they are moving on through hardship life.