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An assessment of palynofacies and sediment data from a core sampled at Harshad estuary, Saurashtra, Gujarat, India was carried out for palaeoenvironmental and palaeoclimatic reconstruction. Drawing on these data we evaluate their relation to cultural/economic changes during the early to late Harappan phases in the peripheral zone of southwest monsoon. Between ca. 5400-5100 yr BP, palynofacies and sediment particle size indicated a high terrestrial influx, interpreted as a period of higher monsoon precipitation. These proxies then indicated a protracted period of diminished freshwater inundation between ca. 5100-1400 yr BP. At the start of this period, archaeobotanical evidence from studied sites in the region also shows the shift in cropping pattern from large grain winter cereals during the Urban Harappan phases to millet based agriculture during the Post-Urban phase, indicating human adaptation in response to climate change. These strategies also appeared contingent on the geographic niche and site type, size and density. The Harshad core from 1400 yr BP to recent times also demonstrates fluctuating precipitation proxies between lower and higher values which may broadly correspond to climate events such as the Medieval Climate Optimum (MCO) and Little Ice Age (LIA), as well reflecting increasing anthropogenic pressures impacting the depositional environment of the estuary.