Abstract: The Ajay is an ephemeral, monsoon influenced river, originated from the Chhotanagpur plateau at Batpar of Jamui, Bihar, flowing through heterogeneous lithology and merge with the river Bhagirathi in West Bengal. Here, an attempt has been made to study the directional relationship between paleo-flow and the present flow direction of the Ajay river in West Bengal. Paleocurrent data help to reconstruct the details of paleo-fluvial system, especially the sedimentary environment of the past. The present work was carried out on the basis of detailed field work at different river segments. In this work, paleo-directional data were obtained from the primary sedimentary structure. Present flow direction data were collected using floats, microform developed on active channel bed and also from sediment grain orientation. By using collected directional data, vector mean of paleo and present flow direction were computed. Analytical results reveal that difference is minimum between present and paleo flow direction in studied segments. The directional relationship between the paleo and the present flow direction was divergent in two segments, convergent in four segments and parallel in three segments. The results help us to understand the sedimentary environment and changing flow regimes of the studied segments. Research highlights: Present and paleo-flow directions of the river are analyzed using vector resultant method.Minimum difference found between present and paleo flow direction of the studied river segments.Sediment successions of the river revealed periodic change in flow character and sediment supply.Natural and anthropogenic factors combinedly affect the flow pattern and sedimentary environment. © 2021, Indian Academy of Sciences.