Migration is an integral part of human history. The Kosi-Seemanchal region of Bihar is a socio-economically backward area dominated by agricultural and allied economic activities, where unemployment and poverty are the principal drivers of out-migration. Inequality in economic development, arising from the uneven spread of the Green Revolution across the region, is the principal cause of large-scale rural out-migration of labour. As economic considerations increasingly shape rural livelihoods, migrant labourers are compelled to search for better wages elsewhere. The development purposive of rapid transportation and communication has further reshaped migration trends and patterns over time. The present paper analyses the trends and changing pattern of labour migration from the Kosi-Seemanchal region. The study is based on primary data collected from 300 migrant labourers through a multi-stage sampling design (selection of Community Development Blocks, followed by random sampling of migrant households within each block) across seven Community Development Blocks of the Kosi-Seemanchal region. The study covers the period 2000-2025, with data analysed at five-year intervals. Descriptive statistics were applied, and MS Excel and ArcGIS software were used to visualise migration flow and the spatial distribution of migrant labor. The results show that migrant labourers are shifting from the traditional destinations of north-western India towards western and southern India. Seasonal migration remains the dominant type of movement in this area, although the pattern is gradually shifting from short-term to longer-term inter-state migration, altering the occupational structure of the population. The large-scale out-migration of labour from the study area is also creating labour scarcity in the region's own farming and construction sectors.