Selenium (Se) is one of the essential micronutrients for performing vital body functions. This study aims at examining the influence of dietary supplementation of garlic clove-based green-synthesized selenium nanoparticles (GBGS-SeNPs, 48-87 nm) on carcass minerals and trace elements, and growth, biochemical, enzymological, and gene expression analyses in the freshwater prawn, Macrobrachium rosenbergii post larvae (PL). The 96 h LC50 of this GBGS-SeNPs to M. rosenbergii PL was 52.23 mg L-1. Five different artificial diets without supplementation of GBGS-SeNPs (control, 0.0 mg kg-1) and with supplementations of GBGS-SeNPs starting from 100 times lower than the LC50 value (0.5, 1.0, 1.5, and 2.0 mg kg-1) were prepared and fed to M. rosenbergii PL for 90 days. A dose-dependent accumulation of Se was observed in the carcass of experimental prawns. GBGS-SeNPs, up to 1.5 mg kg-1 significantly influenced the absorption of other trace elements (Ca, Cu, and Fe) and mineral salts (K, Mg, Na, and Zn). GBGS-SeNPs-supplemented diets showed efficient food conversion ratio (FCR) of 1.32 g against 2.71 g, and therefore enhanced the survival rate (85.6% against 78.8% in control) and weight gain (WG) of 1.41 g against 0.46 g of control prawn. GBGS-SeNPs significantly elevated the activities of protease, amylase, and lipase, and the contents of total protein, essential amino acids (EAA), total carbohydrate, total lipid, monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA), and ash. These indicate the growth promoting potential of GBGS-SeNPs in prawn. The insignificantly altered activities of glutamic oxaloacetate transaminase (GOT), glutamic pyruvate transaminase (GPT), superoxide dismutase (SOD), and catalase, and the content of malondialdehyde (MDA) up to 1.5 mg kg-1 suggest its acceptability in prawn. Moreover, a respective down- and upregulated myostatin (MSTN) and crustacean hyperglycemic hormone (CHH) genes confirmed the influence of GBGS-SeNPs on the growth of prawn. In contrast, 2.0 mg kg-1 GBGS-SeNPs supplementation starts to produce negative effects on prawn (FCR, 1.76 g; survival rate, 82.2%; WG, 0.84 g against respective values of 1.32 g, 85.6%; and 1.41 g observed in 1.5 mg kg-1 of GBGS-SeNPs-supplemented diet fed prawn). This study recommends a maximum of 1.5 mg kg-1 GBGS-SeNPs as dietary supplement to attain sustainable growth of M. rosenbergii. This was confirmed through polynomial and linear regression analyses.