AbstractFragaria × ananassaDuch. (Strawberry) fruit is susceptible to postharvest diseases, thus decrease in quality attributes, such as physiological and biochemical properties leads to decrease in shelf life. The objective of the present study was to check the effect of Selenium NP's and packaging conditions on the shelf life of strawberry (Fragaria × ananassaDuch) fruits. The shelf life was observed with 4 days intervals and examined for characteristics such as physiological weight loss, moisture content, percentage decay loss, peroxidase, catalase, and DPPH radical scavenging. The quality change of postharvestFragaria × ananassaDuch. was monitored by the application of selenium nanoparticles (T1plant extract in 10 mM salt solution, T2plant extract in 30 mM salt solution, T3plant extract in 40 mM salt solution, T4distilled water; control) in different packaging materials (plastic bags, cardboard, and brown paper) at different storage conditions (6°C and 25°C). 10 mM, 20 mM, and 30 mM solution of sodium selenite salt, prepared from 1 M stock solution. Selenium nanoparticles were synthesized usingCassia fistulaL. extract and sodium selenite salt solution. Polyvinyl alcohol (PVA) was used as a stabilizer. The nanoparticles were characterized through UV–visible spectroscopy and X‐Ray diffractometer (XRD). It was observed that the strawberryFragaria × ananassaDuch. Treated with T1(CFE and 10 mM salt solution) stored in plastic packaging at ±6°C showed the best physiological parameters and hence the treatment is recommended for storage without affecting the quality of strawberry fruit up to 16 days.