This paper elaborates the hydrochemical and environmental isotope ($\delta^{2}$H and $\delta^{18}$O) inferences obtained from Uddanam region, Andhra Pradesh, India. Groundwater samples collected during pre-monsoon (June 2019) showed that the quality is fresh (EC < 1539 $\mu$S/cm) and contaminants like fluoride (<1.6 mg/L) and nitrate (<49 mg/L) are present within permissible limits. The composite water quality indices for drinking (DWQI: 14.1–92.5) and irrigation (IWQI: 2.8–20.2) are found to be satisfactory. The major water types are found to be Ca–Na–HCO$_{3}$, Na–Ca–HCO$_{3}$, Na–Mg–HCO$_{3}$–Cl, Ca–Mg–HCO$_{3}$–Cl and Na–HCO$_{3}$. Three geochemical pathways are found signifying evaporite dissolution, contribution of silicate mineral weathering and base-exchange process, which is supported by estimated chloro-alkaline indices (CAI-1: −4.3 to −0.2, CAI-2: −1.03 to −0.08). Trace metal data clearly suggest that groundwater is free from any metal pollution. Dissolved silica (SiO$_{2}$) levels range from 34 to 131 mg/L and do not show any particular spatial trend. Isotope data infer that groundwater is recharged by rainwater after undergoing evaporation ($\delta^{18}$O: −6.0 per thousand), which matches with that of the combined isotope signature ($\delta^{18}$O: −5.5 per thousand) of SW and NE monsoon rainfall. $\delta^{18}$O–TDS correlations and hydrochemical facies evolution (HFE) diagram do not infer any seawater intrusion into these coastal aquifers.

$\bf{Highlights}$

$\bullet$ The composite water quality indices infer good to excellent category for drinking and agriculture.

$\bullet$ Mineral weathering, evaporite dissolution and base-exchange reactions are the main geochemical processes.

$\bullet$ Dissolved silica occurrence in groundwater is sporadic.

$\bullet$ Isotope indicators show the signature of both SW and NE monsoons recharge to groundwater.

$\bullet$ Observed brackishness in groundwater is due to water – rock interaction and not due to sea water intrusion.