Photosynthetically Active Radiation (PAR) plays a critical role in regulating marine primary productivity and air–sea interactions. This study investigates the spatiotemporal variability of PAR over the eastern Arabian Sea (62°E -75°E and 10°N - 25°N) using 21 years (2002–2023) of satellite-derived observations. Monthly PAR data from MODIS-Aqua were analyzed to derive climatology, seasonal cycles, anomalies, and long-term trends. Results reveal pronounced monthly and seasonal variability in PAR in the eastern Arabian Sea. The 21-year averaged monthly PAR time series showed a declining trend for March (p = 0.0061 and Sen’s slope = – 0.04 Einstein m⁻² day⁻¹ yr⁻¹), October (p = 0.009 and Sen’s slope = – 0.11 Einstein m⁻² day⁻¹ yr⁻¹), and December (p = 0.0033 and Sen’s slope = – 0.09 Einstein m⁻² day⁻¹ yr⁻¹) which has the potential to alter primary productivity in these months. Seasonal PAR time series showed maximum during Spring, and a significant decadal decline in Winter (Sen's slope = −0.0535 Einstein m⁻² day⁻¹ yr⁻¹, p = 0.016, Mann-Kendall test). Two decadal Time series investigation of PAR anomaly and Climate mode indices (Niño 3.4 and the Dipole Mode Index) suggests that the Indo-Pacific climate state influences PAR anomalies in the eastern Arabian Sea, but it is not the sole driver. Overall, trend analysis indicates region-specific changes in PAR, with implications for phytoplankton productivity and biogeochemical cycling. The findings highlight the combined influence of atmospheric forcing and ocean dynamics on light availability in the Arabian Sea.