Abstract: Background and Objective: Chlorophylls are essential tetrapyrroles responsible for harvesting solar energy, charge separation and electron transport in photosynthesis. δ-Aminolevulinic acid (ALA) is the common precursor of tetrapyrroles and its synthesis is a key regulatory step in chlorophyll biosynthetic pathway. Selenium is an essential micronutrient for animals and humans but its nutritional requirement in plants is controversial. The effect of Se on ALA synthesis has not been worked out. Thus, the present study was aimed to investigate the effect of Se on ALA synthesizing activity in etiolated maize leaf segments during greening. Materials and Methods: ALA content was estimated by modified Ehrlich’s reagent. ALA content measured after treatment with levulinic acid represents ALA formation. Total chlorophylls were extracted in 80% acetone and then quantitated spectrophotometrically. Student’s t-test was applied to test the significance of difference at probability levels p<0.05, p<0.01and p<0.001. Results: Supply of 0.1 and 0.5 mM Na2SeO3 decreased the ALA content in greening maize leaf segments; however, 0.05 mM Se slightly enhanced its contents. Decline in chlorophyll content was more substantial than decrease in ALA content and carotenoids. Concentration dependent decrease in ALA accumulation was observed with increasing concentration of selenite in light and dark. Substantial difference in ALA accumulation (L-D) was noticed at 0.5 mM Se. Amongst the precursors tested, glutamate and succinate caused more ALA accumulation in -Se tissue in light, while in +Se treated tissue, the increase was prominent by glycine and succinate. When leaf segments were incubated with levulinic acid in light, the ALA formation was increased by GSH in absence of Se; however, it was increased by NADP+ in presence of Se. In dark, GSH stimulated ALA formation, both in the absence and presence of Se. Conclusion: More prominent decrease in total chlorophylls than ALA content/formation with the supply of Se indicates the involvement of other steps of chlorophyll biosynthesis in addition to ALA synthesis, being affected by Se. Substantial decrease in L-D value at higher concentrations of Se suggests that chloroplastic ALA synthesizing activity is more sensitive towards Se.